a327ex.com

EBB Ball Bounce Mechanics

Summary

Built out the physics scaffold for emoji-ball-bounce: a fresh main.lua at the project root porting EBB's collision energy systems faithfully, with single-ball-only adaptations and EBB-faithful directional squash on wall hits. Six energy systems plus two single-ball additions are now active and stable across all ball counts.

Initial assessment and planning:

EBB energy system extraction (emoji-ball-battles/main.lua):

Step 1: bare scaffold (main.lua at root):

Step 2: single-ball energy systems + horizontal-bias kick:

Time-below-half tracking and horizontal-bias kick:

Collision normal convention investigation:

Single-ball bypass system (port of EBB's system 4):

Step 3a: multi-ball spawn keys:

Step 3b/c: ball-ball energy systems (1, 3, 4, 5):

Step 4: visual polish (option A — EBB-faithful only):

EBB audit and spring parameter alignment:

Tuning iterations and user pushback:

Documentation updates at end:

Next steps identified:

Let's continue on Emoji Ball Bounce. Last session we decided on the game's design and now we have to implement it. I believe the decision was to make the arena like Emoji Ball Battles, have balls bouncing around with that energy system, and then build on top of that. Read relevant files, get up to date on everything, and summarize everything to me including our next possible actions.

Bash (ls E:/a327ex/ 2>&1 | head -50)

Anchor/
Anchor-YueScript/
Anchor-lua/
Anchor2/
Danpenzero/
Null/
Orblike/
Psyonia/
RETICLE/
RTFX/
Ricochet/
SNKRX/
a327ex.com-blog/
anchor.blot.im/
cute_action.mp3
cute_action.wav
emoji-ball-battles/
emoji-ball-battles-generated/
emoji-ball-bounce/
it-follows/
lane-battle/
meal_prep.md
music-theory/
notes/
private/
ref1.png
ref2.png
reference/
server.md
thalien-lune/
... [1 more lines]

Bash (ls E:/a327ex/emoji-ball-bounce/ 2>&1)

anchor/
anchor.exe*
assets/
design.md
reference/
run.bat

Bash (ls E:/a327ex/emoji-ball-bounce/reference/ 2>&1; echo "---"; ls E:/a327ex/emoji-b...)

emoji-merge-main/
emojunky-one/
main.lua
super emoji box/
super emoji pop/
super-emoji-box/
super-emoji-invaders/
super-emoji-pop-prototype/
---
ball_wall.ogg
concrete_2.ogg
concrete_5.ogg
concrete_8.ogg
outline.frag
revolver_shot1.ogg
revolver_shot2.ogg
revolver_shot3.ogg
shadow.frag
slight_smile.png
star.png
---
animation.lua
array.lua
camera.lua
class.lua
collider.lua
color.lua
font.lua
helpers.lua
image.lua
... [11 more lines]

Read (E:/a327ex/emoji-ball-bounce/design.md)

1    # Emoji Ball Bounce — design
2   
3   A score-based roguelite. EBB-style physics arena (balls bouncing, optional
4   weapons, energy systems lifted from Emoji Ball Battles). Artifact-style
5   card layer over the top: items attach to balls, improvements sit in the
6   border zones, spells, units, etc. Balatro-style chips × mult scoring at
7   the round level.
8   
9   ## Core loop
10  
11  1. **Draft** before each run: build a starting deck.
12  2. Each **round**: draw N cards, play with available mana, then watch the
13     physics arena run for a fixed timer. Cards generate score from events.
14  3. **Round end:** total score = chips × mult (per-round resolution). If
15     ≥ threshold, advance; threshold scales each round. Otherwise lose.
16  4. Between rounds: shop / draft more cards. Threshold escalates.
17  
18  ## Physics
19  
20  Lifted from Emoji Ball Battles. Open arena (no chamber by default —
21  chambers spawn from cards). Balls bounce, can collide with each other.
22  Optional weapons attach to balls. Gravity on, restitution < 1 plus EBB's
23  energy systems (wall energy boost, floor unstick, ball-ball energy
24  tracking, weapon-weapon boost). Energy must remain stable in **all
25  configurations** — including single ball with no weapons.
26  
27  ## Scoring
28  
29  **Per-round chips × mult.** No default scoring; every chip and every mult
30  comes from a card. Two pools (chips, mult) accumulate over the round
... [92 more lines]

Read (E:/a327ex/emoji-ball-bounce/main.lua)

File does not exist. Note: your current working directory is E:\a327ex.

Bash (ls E:/a327ex/emoji-ball-bounce/ -la 2>&1; echo "---"; ls E:/a327ex/emoji-ball-bo...)

total 4118
drwxr-xr-x 1 adn 197121       0 Apr 26 20:42 ./
drwxr-xr-x 1 adn 197121       0 Apr 25 22:43 ../
drwxr-xr-x 1 adn 197121       0 Apr 26 20:43 .git/
-rw-r--r-- 1 adn 197121     274 Apr 26 20:42 .gitignore
drwxr-xr-x 1 adn 197121       0 Apr 25 22:43 anchor/
-rwxr-xr-x 1 adn 197121 4179968 Apr 25 22:43 anchor.exe*
drwxr-xr-x 1 adn 197121       0 Apr 26 12:37 assets/
-rw-r--r-- 1 adn 197121    5644 Apr 26 20:14 design.md
drwxr-xr-x 1 adn 197121       0 Apr 26 20:25 reference/
-rw-r--r-- 1 adn 197121     151 Apr 25 22:43 run.bat
---
E:/a327ex/emoji-ball-bounce/reference/main.lua

Bash (cd E:/a327ex/emoji-ball-bounce && git log --oneline -20 2>&1)

b847287 Emoji Ball Bounce Exploration

Bash (cd E:/a327ex/emoji-ball-bounce && git status 2>&1)

On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean

Bash (cat E:/a327ex/emoji-ball-bounce/.gitignore 2>&1; echo "---"; cat E:/a327ex/emoji...)

# Third-party reference projects (large, kept locally for context only)
reference/emoji-merge-main/
reference/emojunky-one/
reference/super emoji box/
reference/super emoji pop/
reference/super-emoji-box/
reference/super-emoji-invaders/
reference/super-emoji-pop-prototype/
---
@echo off
REM Run Emoji Ball Bounce. CWD must be repo root; engine receives the game folder name.

cd /d "%~dp0.."
"%~dp0anchor.exe" emoji-ball-bounce

Read (E:/a327ex/emoji-ball-bounce/reference/main.lua)

1    --[[
2     Emoji Ball Bounce — Anchor 2.
3   
4     Variant of Ricochet (ball bouncing inside a square, projectiles spawn on
5     wall hits) using the Emoji Ball Battles visual style: chunky pixel art at
6     480x270/scale=3, sky gradient background, every actor wrapped in a black
7     pixel outline plus a soft drop shadow.
8   
9     This iteration adds the chamber + ball:
10      - chamber rendered as four green rounded-rect "sticks" (emoji-merge
11        arena look) with continuous rotation and [/] resize, ported from
12        Ricochet
13      - ball is the slight_smile emoji at radius 10, bounces inside the
14        chamber at constant speed (Ricochet's velocity-renormalization
15        approach — the simplest thing that keeps a Box2D ball alive)
16  
17    Render pipeline (mirrors EBB, simplified to a single source layer):
18      1. queue draws into game_layer (and bg/ui)
19      2. layer_render(...) flushes queued commands to each layer's FBO
20      3. derive shadow_layer  := game_layer + shadow shader
21         derive game_outline  := game_layer + outline shader
22      4. composite: bg → shadow (offset +4,+4) → outline → game → ui
23  ]]
24  
25  require('anchor')({
26    width  = 640,
27    height = 360,
28    title  = 'Emoji Ball Bounce',
29    scale  = 3,
30    filter = 'rough',
... [866 more lines]

I've read the design doc and the existing scaffold. Let me load AskUserQuestion to batch the decision points at the end.

ToolSearch 

[
  {
    "type": "tool_reference",
    "tool_name": "AskUserQuestion"
  }
]

Summary — Emoji Ball Bounce, where it stands

The vision (from design.md)

A score-based roguelite that fuses three reference points:

Core loop: draft starter deck → each round play cards with mana, watch physics run for a fixed timer, score = chips × mult, beat threshold or lose, threshold escalates.

The hard design problems flagged as open: starting deck composition (avoid chip-only or mult-only soft-locks), mana economy, threshold curve, end-of-round breakdown UI, card pool size (~20–30 across 3–5 archetypes for v1).

Actual state of the repo — important caveat

The repo has one commit ("Emoji Ball Bounce Exploration") and a clean tree. But:

The reference/main.lua itself is from a Ricochet exploration: a single ball bouncing inside a rotating square chamber, projectiles spawn on wall-hits with EBB-style muzzle flashes and capsule projectile-bounce VFX. It uses Ricochet's special-bounce variety mechanic, not EBB's energy systems — so it doesn't match what the design now asks for.

The tension between scaffold and design

The exploration scaffold and the design point in different directions:

scaffold (reference/main.lua) design.md
Arena rotating square chamber, resizable open arena, no chamber by default
Energy Ricochet-style "every Nth bounce, rotate + scale velocity" EBB energy systems (wall boost, floor unstick, ball-ball, weapon-weapon)
Balls one many possible (multi-ball is a card type)
Walls chamber + invisible side walls + top/bottom border top/bottom borders for HUD; balls leave the arena from sides? unclear

So "build on what's there" is partially misleading — the scaffold has solid physics-pipeline plumbing (layers, shaders, projectile VFX, collision drains) that is worth keeping, but the ball energy model needs replacing and the chamber needs to come out of the default state.

Next possible actions — three reasonable paths

  1. Physics rebuild first, scoring layer later. Port EBB's open arena + ball with all four energy systems into a fresh main.lua at root. Reuse the scaffold's render pipeline, projectile system, VFX. Stabilize physics in all configurations (single ball / no weapons / many balls / many weapons) before touching cards. Once the substrate is solid, do the design's "next minimal steps": event bus → chips+mult HUD → 8–12 cards → single-round playtest.

  2. Slim slice end-to-end. Same physics rebuild, but do the minimum energy systems (just wall boost + floor unstick — enough to keep one ball alive forever) and move immediately to the event bus + chips/mult HUD + 3–5 hand-picked cards (one chip source, one mult source, one ×mult, one item, one improvement). Goal: feel a complete loop ASAP, then iterate.

  3. Stay in the scaffold; mutate it. Keep the chamber for now, just retrofit EBB energy systems onto its single ball, and start building the event bus on top of what's there. Move to "open arena" later when the chamber-as-card system goes in. Cheapest first step but accrues rework.

I lean (1) — the design specifically calls out "Energy must remain stable in all configurations — including single ball with no weapons," which is a non-trivial tuning problem. Stabilizing it before cards exist is much cheaper than debugging it through a card layer that's also in flux. The cost: nothing playable for the first chunk of work.

A separate question worth deciding now: do I read EBB's main.lua end-to-end to extract the energy systems verbatim, or do you want to walk me through the systems you actually want lifted (since EBB has more than what we need)?

AskUserQuestion 

User has answered your questions: "Which path should we take for the first work slice?"="Physics rebuild first (Recommended)", "How should I source the EBB energy systems?"="Read EBB main.lua end-to-end (Recommended)", "What should the project's 'main.lua' situation be after this session begins?"="New main.lua at root, leave reference intact (Recommended)". You can now continue with the user's answers in mind.

Reading EBB to extract the energy systems. I'll summarize what I find before writing any code.

Bash (wc -l E:/a327ex/emoji-ball-battles/main.lua 2>&1)

6115 E:/a327ex/emoji-ball-battles/main.lua

Bash (ls E:/a327ex/emoji-ball-battles/docs/ 2>&1)

ATTACK_REFERENCE.md
ENGINE_API.md
ENGINE_API_QUICK.md
FRAMEWORK_API.md
FRAMEWORK_API_QUICK.md
PHASE2_WEAPONS.md
WEAPON_DESIGN.md

Grep (energy)

442:  self.high_speed_hit_count = 0 -- Track recent high speed hits for energy system bypass
446:  -- Energy boost to compensate for Box2D energy loss
447:  self.ball_energy_boost = 1.09
448:  self.weapon_energy_boost = 1.14  -- higher because weapon collisions lose more energy
450:  -- Wall energy boost (fallback system to prevent stalling)
451:  self.system_energy = 250  -- default until first measurement
452:  self.min_wall_energy_boost = 1.0   -- boost at high energy (>=600)
453:  self.max_wall_energy_boost = 1.11 -- boost at very low energy (<=100)
454:  self.wall_energy_boost = 1
562:  COLLISION ENERGY SYSTEM
564:  Box2D leaks energy even with restitution=1, causing balls to eventually stop bouncing.
565:  This system compensates by adding energy on collisions while creating interesting
566:  gameplay dynamics through energy redistribution and pacing control.
568:  1. ENERGY REDISTRIBUTION (keeps both balls active) - ball-ball collisions
569:     Problem: When a fast ball hits a slow ball, energy transfers completely,
571:     Solution: At higher speeds, redistribute energy between balls favoring equal splits.
575:     - Apply @ball_energy_boost (1.09x) to compensate for Box2D energy leakage
581:     lose 30% energy, creating calm moments. Counter resets after bypass.
591:     Problem: System energy can drop too low even with other systems in place.
592:     Solution: Track system_energy (sum of both ball speeds) on ball-ball collisions.
593:     On ball-wall collisions, probabilistically apply energy boost.
594:     - Probability (quad_out): 100% at energy <=100, drops fast to 0% at energy >=600
595:     - Boost value (sine_out): max at energy <=250, drops to 1.0 at energy >=400
603:  6. WEAPON ENERGY BOOST (compensates for weapon collision energy loss) - weapon-weapon collisions
604:     Problem: Weapon collisions drain energy from the system.
605:     Solution: Apply @weapon_energy_boost (1.14x) on weapon-weapon collisions.
663:    -- Update wall energy boost system
664:    self.system_energy = speed_a + speed_b
665:    -- Chance to apply boost: quad_out from 100% at energy 100 to 0% at energy 600
666:    local energy_ratio = math.remap(math.clamp(self.system_energy, 100, 600), 100, 600, 0, 1)
... [42 more lines]

Grep (unstick|stuck|floor_bounce|low_speed|stall)

443:  self.low_horizontal_hit_count = 0 -- Track recent low horizontal hits to prevent stalling
450:  -- Wall energy boost (fallback system to prevent stalling)
583:  3. LOW HORIZONTAL VELOCITY PREVENTION (prevents stalling) - ball-ball collisions
585:     making collisions rare and gameplay stall.
590:  4. WALL FALLBACK (prevents stalling) - ball-wall collisions
597:  5. STUCK BALL DETECTION (prevents floor sliding) - implemented in ball class
601:     apply impulse to unstick it.
760:    -- Track low horizontal velocity collisions to prevent stalling
1173:    -- Skip if stuck in wall
1174:    if projectile_object.kitchen_knife_stuck then goto continue_knife_ball end
1213:    -- Skip if stuck
1214:    if projectile_object.kitchen_knife_stuck then goto continue_knife_weapon end
1294:    if projectile_object.kitchen_knife_stuck then
3871:-- Dash particle: spawns when ball unsticks from floor
4013:    self.kitchen_knife_stuck = false
4145:    if self.kitchen_knife_stuck then
4216:    if self.kitchen_knife_stuck then
4217:      game:push(self.kitchen_knife_stuck_x, self.kitchen_knife_stuck_y, self.kitchen_knife_stuck_angle, s, s)
4265:      self.parent.arena.effects:add(stuck_arrow(self.x + offset*math.cos(angle), self.y + offset*math.sin(angle), {angle = angle}))
4794:-- Stuck arrow: visual-only arrow embedded in a wall
4795:stuck_arrow = object:extend()
4797:function stuck_arrow:new(x, y, args)
4811:function stuck_arrow:update()

Grep (stuck_ball_check|stuck_check|low_speed_check|floor_unstick)

No matches found

Read (E:/a327ex/emoji-ball-battles/main.lua)

540        scale = cloud_base_scale * an.random:float(0.8, 1.2),
541       flip = an.random:sign(),
542       speed = cloud_speed,
543       draw_color = color(255, 255, 255, cloud_alpha),
544       arena_left = cloud_area_x,
545       arena_right = self.x + self.w + 30,
546     })
547     cloud:action(function(self, dt)
548       self.x = self.x + self.speed*dt
549       if self.x > self.arena_right then self.x = self.arena_left - 20 end
550       bg:push(self.x, self.y, 0, self.flip*self.scale, self.scale)
551       bg:image(cloud_image, 0, 0, self.draw_color())
552       bg:pop()
553     end)
554     cloud:flow_to(self)
555   end
556 
557   self.player_ball:start_moving()
558   self.enemy_ball:start_moving()
559 end
560 
561 --[[
562   COLLISION ENERGY SYSTEM
563 
564   Box2D leaks energy even with restitution=1, causing balls to eventually stop bouncing.
565   This system compensates by adding energy on collisions while creating interesting
566   gameplay dynamics through energy redistribution and pacing control.
567 
568   1. ENERGY REDISTRIBUTION (keeps both balls active) - ball-ball collisions
569      Problem: When a fast ball hits a slow ball, energy transfers completely,
... [320 more lines]

Read (E:/a327ex/emoji-ball-battles/main.lua)

880  
881     -- Trigger reflect on melee weapons
882     if ball_a.weapon_class == 'melee' then
883       if ball_a.weapon_ui then ball_a.weapon_ui:reflect() end
884     end
885     if ball_b.weapon_class == 'melee' then
886       if ball_b.weapon_ui then ball_b.weapon_ui:reflect() end
887     end
888   end
889 
890   -- Ball-wall collision: probabilistically apply energy boost based on system energy
891   for _, event in ipairs(an:collision_begin_events('ball', 'wall')) do
892     local ball_object = event.a
893 
894     -- Cancel thrust on wall hit (only after 10% progress to avoid cancelling before it starts)
895     if ball_object.thrusting and ball_object.thrust_progress > 0.1 then
896       ball_object:thrust_end()
897     end
898 
899     local vx, vy = ball_object.collider:get_velocity()
900     if an.random:bool(self.wall_boost_chance) and self.wall_energy_boost > 1 then
901       ball_object.collider:set_velocity(vx*self.wall_energy_boost, vy*self.wall_energy_boost)
902     end
903 
904     -- Squash ball based on wall orientation, intensity shaped by easing
905     local intensity = math.clamp(math.remap(math.length(vx, vy), 0, 800, 0, 1), 0, 1)
906 
907     -- Sound (pitch increases linearly with intensity above 0.45)
908     local pitch
909     if intensity > 0.45 then
... [100 more lines]

Grep (stuck_time|sliding_time|vertical.velocity|vy.5|abs.*vy|unstick)

176:--   wood_heavy_3 (Wood Heavy 8): -25.3 dB -> 0.84
598:     Problem: A ball can lose vertical velocity and slide along a wall indefinitely.
599:     Solution: Each ball tracks how long its vertical velocity stays very low (|vy| < 5)
601:     apply impulse to unstick it.
1268:    an:sound_play("wood_heavy_" .. an.random:int(1, 3), an.random:float(0.46, 0.74), an.random:float(0.95, 1.05))
1750:-- vy_multiplier: |vy| >= 150 = full force, below 150 linearly decreases
1752:  local vy_multiplier = math.min(1, math.remap(math.abs(vy), 0, 150, 0, 1))
1759:      local intensity = math.remap(math.abs(dx), 0, radius, 75, 25)*vy_multiplier
1958:  -- Track low vertical velocity time for sliding detection
1960:  self.low_vy_threshold = an.random:float(0.5, 1.5)
2137:      vertical = vertical - vy*velocity_scale*0.3  -- reduced vertical influence
2213:  -- Low floor detection: if vertical velocity stays low while near the floor, give it a hop
2218:    if self.low_vy_time > self.low_vy_threshold and math.abs(vy) < 15 then
2220:      self.low_vy_threshold = an.random:float(0.5, 1.5)
3871:-- Dash particle: spawns when ball unsticks from floor
4773:  self.vy = math.damping(0.9, 0.5, dt, self.vy)
4846:  self.vy = math.lerp_dt(0.95, 1, dt, self.vy, 0)
4879:  self.vy = math.damping(0.9, 0.5, dt, self.vy)

Read (E:/a327ex/emoji-ball-battles/main.lua)

1955   self.collider:set_restitution(1, self.weapon_sensor)
1956      self.collider:set_density(0, self.weapon_sensor)
1957    
1958      -- Track low vertical velocity time for sliding detection
1959      self.low_vy_time = 0
1960      self.low_vy_threshold = an.random:float(0.5, 1.5)
1961    
1962      -- Initial rotation
1963      self.angle = an.random:angle()
1964      self.collider:set_angle(self.angle)
1965    
1966      -- Angular velocity guardrails (keeps rotation speed balanced for gameplay)
1967      self.time_above_base = 0  -- how long angular velocity has been above base
1968      self.time_below_base = 0  -- how long angular velocity has been below base
1969      self.above_base_grace_period = 0.5  -- seconds before decaying fast spin
1970      self.below_base_grace_period = 0.25  -- seconds before recovering slow spin
1971      self.last_angular_velocity = 0  -- for calculating rotation change from hits
1972    
1973      -- Dagger swing sound tracking (for melee weapons)
1974      self.rotation_accumulator = 0
1975      self.fast_spinning = false
1976      self.swing_sound_count = 0
1977      self.can_swing_sound_time = 1.33  -- starts expired, reset on weapon hits
1978    
1979      -- Springs for visual feedback
1980      self:add(spring())
1981      self.spring:add('hit', 1)
1982      self.spring:add('weapon', 1)
1983      self.spring:add('squash_x', 1)
1984      self.spring:add('squash_y', 1)

Read (E:/a327ex/emoji-ball-battles/main.lua)

2200         if self.rotation_accumulator >= threshold then
2201              self.rotation_accumulator = self.rotation_accumulator - threshold
2202              self.swing_sound_count = self.swing_sound_count + 1
2203              an:sound_play("dagger_swing_" .. an.random:int(1, 5), 0.7, an.random:float(0.95, 1.05))
2204            end
2205          end
2206        else
2207          self.fast_spinning = false
2208          self.rotation_accumulator = 0
2209          self.swing_sound_count = 0
2210        end
2211      end
2212    
2213      -- Low floor detection: if vertical velocity stays low while near the floor, give it a hop
2214      local vx, vy = self.collider:get_velocity()
2215      local near_floor = self.y + self.radius > self.parent.y + self.parent.h - 20
2216      if near_floor then
2217        self.low_vy_time = self.low_vy_time + dt
2218        if self.low_vy_time > self.low_vy_threshold and math.abs(vy) < 15 then
2219          self.low_vy_time = 0
2220          self.low_vy_threshold = an.random:float(0.5, 1.5)
2221          self.collider:apply_impulse(math.sign(vx)*an.random:float(0, 6), -24)
2222          -- Sound
2223          an:sound_play('hop', 0.5, an.random:float(0.95, 1.05))
2224          -- Squash horizontally, stretch vertically (opposite of floor hit)
2225          self.spring:pull('squash_y', 0.5, 3, 0.5)
2226          self.spring:pull('squash_x', -0.25, 3, 0.5)
2227          -- Spawn dash particle at ball's bottom, direction opposite to velocity
2228          local particle_angle = math.remap(vx, -100, 100, math.pi/4, 3*math.pi/4) + an.random:float(-math.pi/8, math.pi/8)
2229          self.parent.effects:add(dash_particle(self.x, self.y + self.radius, {direction = particle_angle}))
... [30 more lines]

Grep (max_ball_speed|max_angular_velocity)

444:  self.max_ball_speed = 448
606:     Also cap linear speed at @max_ball_speed and angular velocity at ball.max_angular_velocity.
608:  Speed is capped at @max_ball_speed to prevent things from getting too chaotic.
678:    -- Track high speed hits (either ball > 0.78*@max_ball_speed)
679:    local is_high_speed_hit = max_speed > 0.78*self.max_ball_speed
700:      local speed_ratio = math.remap(max_speed, 0, self.max_ball_speed, 0, 1)
745:    -- Cap speed at @max_ball_speed
747:    if speed_a > self.max_ball_speed then
748:      local scale = self.max_ball_speed/speed_a
754:    if speed_b > self.max_ball_speed then
755:      local scale = self.max_ball_speed/speed_b
761:    local is_low_horizontal = math.abs(vx_a) + math.abs(vx_b) < 0.25*self.max_ball_speed
816:    -- Cap speed at @max_ball_speed
818:    if speed_a > self.max_ball_speed then
819:      local scale = self.max_ball_speed/speed_a

[Showing results with pagination = limit: 15]

Read (E:/a327ex/emoji-ball-battles/main.lua)

430    -- Create balls
431   local headless_player_weapon = args.player_weapon or 'cd'
432   local headless_enemy_weapon = args.enemy_weapon or 'bow'
433   self.player_ball = ball(self.x + self.w*0.25, self.y + self.h/2, 'player', headless_player_weapon)
434   self.enemy_ball = ball(self.x + self.w*0.75, self.y + self.h/2, 'enemy', headless_enemy_weapon)
435   self:add(self.player_ball)
436   self:add(self.enemy_ball)
437 
438   -- Create plants container and spawn plant groups
439   self:add(object('plants'))
440   self:spawn_plants()
441 
442   self.high_speed_hit_count = 0 -- Track recent high speed hits for energy system bypass
443   self.low_horizontal_hit_count = 0 -- Track recent low horizontal hits to prevent stalling
444   self.max_ball_speed = 448
445 
446   -- Energy boost to compensate for Box2D energy loss
447   self.ball_energy_boost = 1.09
448   self.weapon_energy_boost = 1.14  -- higher because weapon collisions lose more energy
449 
450   -- Wall energy boost (fallback system to prevent stalling)
451   self.system_energy = 250  -- default until first measurement
452   self.min_wall_energy_boost = 1.0   -- boost at high energy (>=600)
453   self.max_wall_energy_boost = 1.11 -- boost at very low energy (<=100)
454   self.wall_energy_boost = 1
455   self.wall_boost_chance = 0  -- probability of applying boost (0-100)
456 
457   -- Hit timing system (for scaling hit effects and hit stop)
458   self.time_since_last_hit = 1.5  -- start at max so first hit is full intensity
459 
... [90 more lines]

Grep (^function ball:new|self.collider = collider|set_gravity_scale|set_restitution|set_friction|set_density|set_linear_damping)

1025:      projectile_object.collider:set_gravity_scale(2)
1768:function ball:new(x, y, team, weapon_type)
1944:  self.collider:set_restitution(1)
1945:  self.collider:set_friction(0)
1946:  self.collider:set_linear_damping(0)
1951:  self.collider:set_restitution(1, self.weapon_shape)
1952:  self.collider:set_density(0, self.weapon_shape)
1955:  self.collider:set_restitution(1, self.weapon_sensor)
1956:  self.collider:set_density(0, self.weapon_sensor)
2021:  self.collider:set_gravity_scale(0)
2590:    self.collider:set_gravity_scale(0)
2605:  self.collider:set_gravity_scale(1)
2925:  self.collider:set_gravity_scale(1)
3948:    self.collider:set_restitution(0.75)
3949:    self.collider:set_friction(0)
3950:    self.collider:set_gravity_scale(0.5)
3952:    self.collider:set_density(0.4)
3958:    self.collider:set_restitution(0)
3959:    self.collider:set_friction(1)
3960:    self.collider:set_gravity_scale(0)
3962:    self.collider:set_density(0.1)
3975:    self.collider:set_restitution(0)
3976:    self.collider:set_friction(0)
3977:    self.collider:set_gravity_scale(0)
3978:    self.collider:set_density(0.4)
3999:    self.collider:set_gravity_scale(0)
4000:    self.collider:set_friction(0)
4001:    self.collider:set_density(0.1)
4020:    self.collider:set_gravity_scale(0.5)
4021:    self.collider:set_restitution(0.4)
... [12 more lines]

Read (E:/a327ex/emoji-ball-battles/main.lua)

1925     self.weapon_hitbox_length = 16
1926        self.weapon_hitbox_width = 16
1927        self.weapon_scale = 18/512
1928        self.weapon_scale_y = 18/512
1929        self.weapon_rotation_offset = 0
1930        self.base_angular_velocity = 1.5*math.pi
1931        self.max_angular_velocity = 3*math.pi
1932        self.weapon_weight = 1.0
1933        self.hit_stop_multiplier = 1.0
1934        self.hit_particle_multiplier = 1.0
1935        self.camera_shake_multiplier = 1.0
1936        self.cd_cooldown = 3.75
1937        self.cd_base_bounces = 1
1938        self.cd_bonus_bounces = 0
1939        self.cd_speed = 157
1940      end
1941    
1942      self:add(collider('ball', 'dynamic', 'circle', self.radius))
1943      self.collider:set_position(self.x, self.y)
1944      self.collider:set_restitution(1)
1945      self.collider:set_friction(0)
1946      self.collider:set_linear_damping(0)
1947    
1948      -- Add weapon hitbox (physical, 0 density so it doesn't affect ball mass/inertia)
1949      local hitbox_oy = self.weapon_hitbox_offset_y or 0
1950      self.weapon_shape = self.collider:add_box('weapon', self.weapon_hitbox_length, self.weapon_hitbox_width, {offset_x = self.weapon_hitbox_offset, offset_y = hitbox_oy})
1951      self.collider:set_restitution(1, self.weapon_shape)
1952      self.collider:set_density(0, self.weapon_shape)
1953      -- Add sensor for detecting ball overlaps (passes through balls, generates events)
1954      self.weapon_sensor = self.collider:add_box('weapon_hitbox', self.weapon_hitbox_length, self.weapon_hitbox_width, {offset_x = self.weapon_hitbox_offset, offset_y = hitbox_oy, sensor = true})
... [5 more lines]

Grep (^function arena:|self.gravity|physics_gravity|set_gravity|world_gravity)

249:an:physics_set_gravity(0, 384)
400:function arena:new(args)
610:function arena:early_update(dt)
1025:      projectile_object.collider:set_gravity_scale(2)
1536:function arena:update(dt)
1575:function arena:get_hit_stop_probability()
1584:function arena:hit_effect(x, y, multiplier)
1600:function arena:hit_stop(duration)
1610:function arena:spawn_plants()
1655:function arena:fill_plant_gaps(spawned, floor_y)
1705:function arena:spawn_plant_group(index, x, y)
1751:function arena:apply_direct_force_to_nearby_plants(x, y, radius, vy)
2021:  self.collider:set_gravity_scale(0)
2590:    self.collider:set_gravity_scale(0)
2605:  self.collider:set_gravity_scale(1)
2925:  self.collider:set_gravity_scale(1)
3411:  self.gravity_velocity = 0
3412:  self.gravity = args.gravity or 0
3431:  self.gravity_velocity = self.gravity_velocity + self.gravity*dt
3434:  local vy = self.velocity*math.sin(self.direction) + self.gravity_velocity
3793:  self.gravity_velocity = 0
3794:  self.gravity_acceleration = args.gravity or 0
3812:  self.gravity_velocity = self.gravity_velocity + self.gravity_acceleration*dt
3816:  local vy = self.velocity*math.sin(self.direction) + self.gravity_velocity
3950:    self.collider:set_gravity_scale(0.5)
3960:    self.collider:set_gravity_scale(0)
3977:    self.collider:set_gravity_scale(0)
3999:    self.collider:set_gravity_scale(0)
4020:    self.collider:set_gravity_scale(0.5)
4037:    self.collider:set_gravity_scale(0)
... [2 more lines]

Read (E:/a327ex/emoji-ball-battles/main.lua)

240  an:sound('cd_throw_3', 'assets/cd_throw_3.ogg')
241 an:sound('cd_wall_1', 'assets/cd_wall_1.ogg')
242 an:sound('cd_wall_2', 'assets/cd_wall_2.ogg')
243 an:sound('cd_wall_3', 'assets/cd_wall_3.ogg')
244 an:music('bgm', 'assets/batoru_umi_to_mamono_no_kodomo_tachi.ogg')
245 an:music('enbudai', 'assets/enbudai.ogg')
246 an:music_set_volume(0.8)
247 
248 an:physics_init()
249 an:physics_set_gravity(0, 384)
250 an:physics_tag('wall')
251 an:physics_tag('ball')
252 an:physics_tag('weapon')
253 an:physics_tag('weapon_hitbox')
254 an:physics_tag('plant_ghost')
255 an:physics_tag('projectile')
256 an:physics_collision('ball', 'wall')
257 an:physics_collision('ball', 'ball')
258 an:physics_collision('weapon', 'weapon')
259 an:physics_tag('projectile_sensor')
260 an:physics_collision('projectile', 'wall')
261 an:physics_collision('projectile', 'weapon')
262 an:physics_sensor('projectile_sensor', 'ball')
263 an:physics_sensor('projectile_sensor', 'plant_ghost')
264 an:physics_tag('spiral_projectile')
265 an:physics_collision('spiral_projectile', 'wall')
266 an:physics_tag('spiral_weapon_sensor')
267 an:physics_sensor('spiral_weapon_sensor', 'weapon')
268 an:physics_tag('boomerang_projectile')
269 an:physics_collision('boomerang_projectile', 'wall')
... [50 more lines]

Read (E:/a327ex/emoji-ball-battles/main.lua)

400  function arena:new(args)
401   args = args or {}
402   object.new(self, 'arena')
403 
404   -- headless: seed RNG for deterministic battles
405   if args.seed then
406     an.random:set_seed(args.seed)
407   end
408 
409   self:add(object('effects'))
410   self:add(object('projectiles'))
411   self:add(timer())
412 
413   -- CD wall hit volume decay: volume decreases with rapid hits, recovers over 2 seconds
414   self.cd_wall_volume = 1.0
415   self.cd_wall_volume_recovery_rate = 0.3/2  -- recovers 0.3 over 2 seconds
416 
417   -- Play area dimensions (200x200, centered)
418   self.w, self.h = 200, 200
419   self.x = (gw - self.w)/2
420   self.y = (gh - self.h)/2
421   local wall_thickness = 200
422 
423   -- Create walls as children (top, bottom/floor, left, right)
424   -- Floor is only arena width; side walls extend down to cover the rest
425   self:add(wall(self.x + self.w/2, self.y - wall_thickness/2, self.w + wall_thickness*2, wall_thickness))
426   self:add(wall(self.x + self.w/2, self.y + self.h + wall_thickness/2, self.w, wall_thickness, nil, true))
427   self:add(wall(self.x - wall_thickness/2, self.y + self.h/2 + wall_thickness/2, wall_thickness, self.h + wall_thickness))
428   self:add(wall(self.x + wall_thickness/2 + self.w, self.y + self.h/2 + wall_thickness/2, wall_thickness, self.h + wall_thickness))
429 
... [5 more lines]

Grep (^function wall:new|wall.*restitution)

4896:function wall:new(x, y, w, h, col, is_floor)

Read (E:/a327ex/emoji-ball-battles/main.lua)

4896 function wall:new(x, y, w, h, col, is_floor)
4897      self.x, self.y = x, y
4898      self.w, self.h = w, h
4899      self.color = col or wall_color()
4900      self.is_floor = is_floor or false
4901      object.new(self)
4902      self:add(collider('wall', 'static', 'box', self.w, self.h))
4903      self.collider:set_position(self.x, self.y)
4904      self.collider:set_restitution(1)
4905    end
4906    
4907    function wall:update()
4908      game:rectangle(self.x - self.w/2, self.y - self.h/2, self.w, self.h, self.color)
4909      -- Draw green cover to hide plant roots
4910      if self.is_floor then
4911        cover:rectangle(self.x - self.w/2, self.y - self.h/2, self.w, self.h, self.color)
4912      end
4913    end
4914    
4915    
4916    -- Move non-report files from results/ to generated mirror
4917    -- Keeps .html (reports) and .dat (needed for report regeneration) in place
4918    function headless_move_intermediate_files()
4919      local gen_results = "E:/a327ex/emoji-ball-battles-generated/results"
4920      os.execute("mkdir \"E:/a327ex/emoji-ball-battles-generated\" 2>nul")
4921      os.execute("mkdir \"" .. gen_results .. "\" 2>nul")
4922      os.execute("for %f in (results\\*.lua) do move /Y \"%f\" \"" .. gen_results .. "\\\" >nul 2>nul")
4923      os.execute("for %f in (results\\*.tmp) do move /Y \"%f\" \"" .. gen_results .. "\\\" >nul 2>nul")
4924      os.execute("for %f in (results\\*.dat) do move /Y \"%f\" \"" .. gen_results .. "\\\" >nul 2>nul")
4925      print("Intermediate files moved to: " .. gen_results)
... [10 more lines]

Bash (grep -n "^function" E:/a327ex/emoji-ball-bounce/anchor/collider.lua 2>&1 | head ...)

35:function collider:new(owner, tag, body_type, shape_type, ...)
73:function collider:destroy()
85:function collider:sync()
92:function collider:get_position() return physics_get_position(self.body) end
93:function collider:set_position(x, y) physics_set_position(self.body, x, y) end
94:function collider:get_angle() return physics_get_angle(self.body) end
95:function collider:set_angle(angle) physics_set_angle(self.body, angle) end
98:function collider:get_velocity() return physics_get_velocity(self.body) end
99:function collider:set_velocity(vx, vy) physics_set_velocity(self.body, vx, vy) end
100:function collider:get_angular_velocity() return physics_get_angular_velocity(self.body) end
101:function collider:set_angular_velocity(av) physics_set_angular_velocity(self.body, av) end
104:function collider:apply_force(fx, fy) physics_apply_force(self.body, fx, fy) end
105:function collider:apply_force_at(fx, fy, px, py) physics_apply_force_at(self.body, fx, fy, px, py) end
106:function collider:apply_impulse(ix, iy) physics_apply_impulse(self.body, ix, iy) end
107:function collider:apply_impulse_at(ix, iy, px, py) physics_apply_impulse_at(self.body, ix, iy, px, py) end
108:function collider:apply_torque(torque) physics_apply_torque(self.body, torque) end
109:function collider:apply_angular_impulse(impulse) physics_apply_angular_impulse(self.body, impulse) end
112:function collider:set_linear_damping(damping) physics_set_linear_damping(self.body, damping) end
113:function collider:set_angular_damping(damping) physics_set_angular_damping(self.body, damping) end
114:function collider:set_gravity_scale(scale) physics_set_gravity_scale(self.body, scale) end
115:function collider:set_fixed_rotation(fixed) physics_set_fixed_rotation(self.body, fixed) end
116:function collider:set_bullet(bullet) physics_set_bullet(self.body, bullet) end
119:function collider:set_friction(friction, shape) physics_shape_set_friction(shape or self.shape, friction) end
120:function collider:get_friction(shape) return physics_shape_get_friction(shape or self.shape) end
121:function collider:set_restitution(restitution, shape) physics_shape_set_restitution(shape or self.shape, restitution) end
122:function collider:get_restitution(shape) return physics_shape_get_restitution(shape or self.shape) end
123:function collider:set_density(density, shape) physics_shape_set_density(shape or self.shape, density) end
124:function collider:get_density(shape) return physics_shape_get_density(shape or self.shape) end
125:function collider:set_filter_group(group, shape) physics_shape_set_filter_group(shape or self.shape, group) end
126:function collider:destroy_shape(shape, update_mass)

Bash (grep -n "collision_entities_begin|random_int|random_float|random_normal|math...)

E:/a327ex/emoji-ball-bounce/anchor/array.lua:416:    return t[random_int(1, #t, rng)]
E:/a327ex/emoji-ball-bounce/anchor/array.lua:421:      local i = random_int(1, #t, rng)
E:/a327ex/emoji-ball-bounce/anchor/array.lua:473:    return table.remove(t, random_int(1, #t, rng))
E:/a327ex/emoji-ball-bounce/anchor/array.lua:477:      table.insert(out, table.remove(t, random_int(1, #t, rng)))
E:/a327ex/emoji-ball-bounce/anchor/array.lua:559:    local j = random_int(1, i, rng)
E:/a327ex/emoji-ball-bounce/anchor/camera.lua:196:    c.x = math.lerp_dt(c.follow_lerp, c.follow_lerp_time, dt, c.x, tx)
E:/a327ex/emoji-ball-bounce/anchor/camera.lua:197:    c.y = math.lerp_dt(c.follow_lerp, c.follow_lerp_time, dt, c.y, ty)
E:/a327ex/emoji-ball-bounce/anchor/collider.lua:195:    dx, dy = dx*math.remap(d, 0, rs, 0, max_speed), dy*math.remap(d, 0, rs, 0, max_speed)
E:/a327ex/emoji-ball-bounce/anchor/collider.lua:228:  self.wander_r = self.wander_r + random_float(-jitter*dt, jitter*dt)
E:/a327ex/emoji-ball-bounce/anchor/math.lua:44:    math.lerp(0.5, 0, 100)   -> 50
E:/a327ex/emoji-ball-bounce/anchor/math.lua:45:    math.lerp(0, 0, 100)     -> 0
E:/a327ex/emoji-ball-bounce/anchor/math.lua:46:    math.lerp(1, 0, 100)     -> 100
E:/a327ex/emoji-ball-bounce/anchor/math.lua:55:function math.lerp(t, source, destination)
E:/a327ex/emoji-ball-bounce/anchor/math.lua:63:    x = math.lerp_dt(0.9, 1, dt, x, target)   -> covers 90% of distance in 1 second
E:/a327ex/emoji-ball-bounce/anchor/math.lua:64:    x = math.lerp_dt(0.5, 0.5, dt, x, target)  -> covers 50% of distance in 0.5 seconds
E:/a327ex/emoji-ball-bounce/anchor/math.lua:79:function math.lerp_dt(p, t, dt, source, destination)
E:/a327ex/emoji-ball-bounce/anchor/math.lua:80:  return math.lerp(1 - (1 - p)^(dt/t), source, destination)
E:/a327ex/emoji-ball-bounce/anchor/math.lua:128:    math.lerp_angle(0.5, 0, math.pi)          -> math.pi/2
E:/a327ex/emoji-ball-bounce/anchor/math.lua:129:    math.lerp_angle(0.5, -math.pi, math.pi)   -> 0 (takes shortest path)
E:/a327ex/emoji-ball-bounce/anchor/math.lua:142:function math.lerp_angle(t, source, destination)
E:/a327ex/emoji-ball-bounce/anchor/math.lua:152:    angle = math.lerp_angle_dt(0.9, 1, dt, angle, target_angle)
E:/a327ex/emoji-ball-bounce/anchor/math.lua:167:function math.lerp_angle_dt(p, t, dt, source, destination)
E:/a327ex/emoji-ball-bounce/anchor/math.lua:168:  return math.lerp_angle(1 - (1 - p)^(dt/t), source, destination)
E:/a327ex/emoji-ball-bounce/anchor/math.lua:232:    math.remap(10, 0, 20, 0, 1)        -> 0.5 (10 is 50% of [0, 20], maps to 50% of [0, 1])
E:/a327ex/emoji-ball-bounce/anchor/math.lua:233:    math.remap(3, 0, 3, 0, 100)        -> 100

Bash (grep -n "function math." E:/a327ex/emoji-ball-bounce/anchor/math.lua | head -40...)

55:function math.lerp(t, source, destination)
79:function math.lerp_dt(p, t, dt, source, destination)
98:function math.damping(p, t, dt, v)
120:function math.loop(t, length)
142:function math.lerp_angle(t, source, destination)
167:function math.lerp_angle_dt(p, t, dt, source, destination)
184:function math.sign(value)
203:function math.length(x, y)
222:function math.clamp(value, min, max)
250:function math.remap(value, old_min, old_max, new_min, new_max)
269:function math.angle(x, y)
287:function math.angle_to_point(x1, y1, x2, y2)
304:function math.distance(x1, y1, x2, y2)
323:function math.normalize(x, y)
345:function math.direction(angle)
363:function math.rotate(x, y, angle)
387:function math.reflect(angle, normal_x, normal_y)
415:function math.snap(value, grid)
437:function math.limit(x, y, max)
448:function math.linear(t) return t end
451:function math.sine_in(t)
457:function math.sine_out(t)
463:function math.sine_in_out(t)
469:function math.sine_out_in(t)
477:function math.quad_in(t) return t*t end
479:function math.quad_out(t) return -t*(t - 2) end
481:function math.quad_in_out(t)
490:function math.quad_out_in(t)
501:function math.cubic_in(t) return t*t*t end
503:function math.cubic_out(t)
... [10 more lines]

Bash (grep -n "^function random|^random_normal|function math.normal|random:normal"...)

E:/a327ex/emoji-ball-bounce/anchor/math.lua:323:function math.normalize(x, y)

Bash (grep -n "^function random|^function physics|^function collision" E:/a327ex/emo...)

E:/a327ex/emoji-ball-bounce/anchor/physics.lua:137:function collision_entities_begin(tag_a, tag_b)
E:/a327ex/emoji-ball-bounce/anchor/physics.lua:164:function collision_entities_end(tag_a, tag_b)

Bash (grep -rn "^random_int|^random_float|^random_angle|^random_bool|^random_sign"...)

(Bash completed with no output)

Grep (function random_(int|float|angle|bool|sign|normal))

No matches found

Grep (random_int\b|random_float\b|random_angle\b|random_bool\b|random_normal\b|random_sign\b)

E:\a327ex\emoji-ball-bounce\anchor\array.lua:416:    return t[random_int(1, #t, rng)]
E:\a327ex\emoji-ball-bounce\anchor\array.lua:421:      local i = random_int(1, #t, rng)
E:\a327ex\emoji-ball-bounce\anchor\array.lua:473:    return table.remove(t, random_int(1, #t, rng))
E:\a327ex\emoji-ball-bounce\anchor\array.lua:477:      table.insert(out, table.remove(t, random_int(1, #t, rng)))
E:\a327ex\emoji-ball-bounce\anchor\array.lua:559:    local j = random_int(1, i, rng)
E:\a327ex\emoji-ball-bounce\anchor\collider.lua:228:  self.wander_r = self.wander_r + random_float(-jitter*dt, jitter*dt)
E:\a327ex\emoji-ball-bounce\anchor\shake.lua:263:        inst.current_x = decay*inst.amplitude*random_float(-1, 1)
E:\a327ex\emoji-ball-bounce\anchor\shake.lua:264:        inst.current_y = decay*inst.amplitude*random_float(-1, 1)

Grep (random_normal|"normal"|random:normal)

7588:// random_normal(mean?, stddev?, rng?) - Gaussian distribution via Box-Muller transform
7589:static int l_random_normal(lua_State* L) {
8972:    lua_register(L, "random_normal", l_random_normal);

I have everything I need. Here is what I've extracted from EBB and how I'd port it. No code yet — I want to surface the plan and the design tension before writing anything.

What EBB's "energy system" actually is

EBB sets restitution = 1 on both ball and walls. Box2D combines restitutions via max(), so collisions are theoretically perfectly elastic — but in practice Box2D still leaks energy through constraint solver imprecision. EBB compensates with six small subsystems, not four. They live almost entirely inside collision-event handlers in arena:early_update. Constants worth knowing: MAX_BALL_SPEED = 448, WORLD_GRAVITY_Y = 384, ball uses friction = 0, linear_damping = 0, gravity_scale = 1. Arena is 200×200, walls are 200-thick rectangles wrapped around the play area so corners are sealed.

# What When it fires What it does
1 Ball energy boost (1.09×) every ball-ball collision multiplies both balls' velocities by 1.09× to claw back Box2D's per-collision leakage
2 Wall energy boost (≤1.11×) ball-wall collisions, probabilistically tracks system_energy (sum of ball speeds, updated on ball-ball collisions). Probability shaped by quad_out: 100% at energy ≤ 100, 0% at ≥ 600. Boost magnitude shaped by sine_out: 1.11× at ≤ 250 → 1.0× at ≥ 400. The fallback that prevents single-system stalls.
3 Energy redistribution every ball-ball collision, probabilistically at higher relative speeds, redistributes energy between balls toward equal split using random_normal(0.5, stddev) where stddev shrinks 0.3 → 0.1 with speed. Counters the "fast ball ping-ponging slow ball" failure mode.
4 High-speed bypass ball-ball, S-curve probability counts consecutive high-speed hits (>0.78×MAX). Probability cubic_in_out(count/9), guaranteed at 9. When it fires, multiplies both velocities by 0.7 — a deliberate "calm down" beat for pacing.
5 Low-horizontal prevention ball-ball, linear probability counts hits where |vx_a| + |vx_b| < 0.25×MAX. Linear chance, guaranteed at 4. Triggers a random horizontal impulse (100–200, random sign) on both balls.
6 Stuck-ball detection every ball update when the ball is near_floor (within 20 px of floor) and |vy| < 15, accumulate low_vy_time. After a random 0.5–1.5 s threshold, apply (sign(vx)*rand(0,6), -24) impulse — the "hop". Per-ball, not collision-driven.
(7) Weapon energy boost (1.14×) weapon-weapon parries parry-only; skip for v1 since we have no weapons yet.

After every collision-driven energy modification, EBB caps speed at MAX_BALL_SPEED by scaling velocity down. We need that everywhere too.

The single-ball stability problem (this is the real risk)

The design says "Energy must remain stable in all configurations — including single ball with no weapons." EBB itself was never tested in this configuration, and looking at the code:

So when porting, I need to change system 2 to update system_energy from the actual current ball speeds every frame (or on every ball-wall collision), summed across all live balls. That's a one-line change but it's load-bearing for single-ball stability. I'd want to verify experimentally that single-ball + multi-ball both reach a stable equilibrium before declaring it done.

Proposed v0 main.lua at root

What I'd build:

A few questions worth asking before I write code

AskUserQuestion 

User has answered your questions: "Should ball count be fixed for v0 or runtime-changeable?"="Spawn key (1-9 balls)", "Keep projectile-on-wall-hit?"="Remove for v0", "Where should arena boundaries live?"="The arena should match the Emoji Ball Battles arena exactly in terms of layout.", "How aggressive should the debug HUD be?"="There should be no debug HUD for now.". You can now continue with the user's answers in mind.

Grep (^require(.anchor.)|width\s=|height\s=|scale\s*=)

1:require('anchor')({ width = 480, height = 270, scale = 3 })
471:  local cloud_base_scale = 24/cloud_image.width
540:      scale = cloud_base_scale * an.random:float(0.8, 1.2),
624:    if an.time_scale == 0 then
625:      an.time_scale = 1
627:      an.time_scale = 0
748:      local scale = self.max_ball_speed/speed_a
755:      local scale = self.max_ball_speed/speed_b
819:      local scale = self.max_ball_speed/speed_a
826:      local scale = self.max_ball_speed/speed_b
1231:      scale = projectile_object.kitchen_knife_scale,
1342:          scale = an.random:float(0.8, 1.2),
1379:            scale = an.random:float(0.8, 1.2),
1590:    self.effects:add(hit_effect(x, y, {scale = 1.35*multiplier}))
1776:  self.scale = 2*self.radius/self.image.width
1778:    self.scale = 1.125*self.scale
1793:    self.weapon_scale = 18/512 -- gun.png is 512x512
1811:    self.weapon_scale = 32/512 -- sword.png is 512x512
1834:    self.weapon_scale = -26/512
1861:    self.weapon_scale = 18/512  -- dagger.png is 512x512
1880:    self.weapon_scale = 22/512
1901:    self.weapon_scale = 22/512
1927:    self.weapon_scale = 18/512
2125:      local horizontal_scale = dir == 1 and (0.35 + 0.65*math.cos(self.angle)) or (0.35 - 0.65*math.cos(self.angle))
2135:      local velocity_scale = 0.001  -- scale factor for velocity influence
2143:      flame.velocity_height_scale = 1.6/(1 + math.exp(-(speed - 1.73)))
2238:  local hit_scale = self.spring.hit.x
2322:    local string_scale = bow_stretch*weapon_spring
2350:      local arrow_scale = 26/512
2439:              scale = an.random:float(0.8, 1.2),
... [2 more lines]

Grep (wall_color|wall.*color\b)

24:wall_color = fg:clone():mix(yellow, 0.1)
4899:  self.color = col or wall_color()

Read (E:/a327ex/emoji-ball-battles/main.lua)

15   star_yellow = color(255, 172, 51)
16  orange = color(244, 146, 0)
17  blue = color(83, 175, 239)
18  green = color(122, 179, 87)
19  red = color(223, 37, 64)
20  purple = color(172, 144, 216)
21  brown = color(193, 105, 79)
22  bowstring = color(217, 158, 130)
23  debug_draw_enabled = false
24  wall_color = fg:clone():mix(yellow, 0.1)
25  
26  -- Sky colors (subtle blue gradient)
27  sky_top = color(135, 206, 235)     -- light sky blue
28  sky_bottom = color(231, 232, 233)  -- same as fg (off-white)
29  
30  -- Camera (must be created before layers, which default to an.camera)
31  an:add(camera(gw, gh))
32  an.camera:add(shake())
33  an.camera.shake:handcam(true, {x = 2, y = 2, rotation = 0.02}, 0.5)
34  
35  -- Layers
36  bg = an:layer('bg')
37  back = an:layer('back')
38  back_outline = an:layer('back_outline')
39  game = an:layer('game')
40  game_outline = an:layer('game_outline')
41  front = an:layer('front')
42  front_outline = an:layer('front_outline')
43  cover = an:layer('cover')
44  weapons = an:layer('weapons')

Bash (grep -n "function.:mix|function.:clone" E:/a327ex/emoji-ball-bounce/anchor/co...)

(Bash completed with no output)

Read (E:/a327ex/emoji-ball-bounce/anchor/color.lua)

1    --[[
2     color — mutable RGBA color with HSL conversion helpers.
3   
4     Simpler than v1's color class. A color is a plain table {r, g, b, a} with
5     a __call metamethod that returns the packed rgba integer used by drawing
6     functions. No auto-sync between RGB and HSL — HSL is a *conversion*, not a
7     storage format. If you want to modify hue, convert to HSL, modify, convert
8     back.
9   
10    Usage:
11      red = color_new(255, 0, 0)
12      red.a = 128              -- set alpha
13      layer:circle(x, y, r, red())  -- __call returns packed rgba integer
14  
15      -- HSL manipulation:
16      h, s, l = color_to_hsl(red)
17      h = (h + 120) % 360      -- shift hue
18      shifted = color_from_hsl(h, s, l, red.a)
19  
20      -- Common operations:
21      copy = color_clone(red)
22      mixed = color_mix(red, blue, 0.5)
23      dark = color_darken(red, 0.5)      -- multiply RGB by 0.5
24      light = color_lighten(red, 1.5)    -- multiply RGB by 1.5 (clamped)
25      inverted = color_invert(red)
26  
27    Design notes:
28      - Colors are plain tables. Modify fields directly: c.r = 100.
29      - Procedural functions (color_mix, color_clone, etc.) return NEW colors,
30        not mutating the input. If you want to mutate, do `c.r = ...` directly.
... [151 more lines]

Locked-in plan

Pulling it together based on your answers:

Recommended incremental rollout

Per CLAUDE.md ("one method at a time, small incremental changes"), I'd suggest splitting the work into three runnable checkpoints rather than dropping the whole file at once:

  1. Bare scaffold — engine init, layers, sky bg, walls, single ball, render loop. No energy systems. Ball bounces and slowly bleeds energy via Box2D leakage. This verifies layer pipeline + walls + ball physics in isolation.
  2. Energy systems on — add all 6 systems, plus the system_energy per-frame update fix. Single ball should now sustain indefinitely. Test by leaving it running.
  3. Multi-ball spawn — add space / backspace bindings + spawn helper. Test 2/5/9 balls all stable simultaneously.

Each checkpoint is a discrete, runnable, testable change. If something feels off at step 2 (especially the single-ball case), we tune before adding multi-ball complexity.

Two things I want you to push back on if you disagree

  1. Resolution change from 640×360 → 480×270. Reference scaffold is 640×360. The CLAUDE.md note about Emoji Ball Battles + "match EBB exactly" suggests 480×270, but this changes the visible game size. If you want 640×360 with the EBB arena scaled up proportionally (so 200×200 → ~267×267), say so.
  2. fixed_rotation = true on the ball. EBB doesn't fix rotation because weapons need to spin. We have no weapons in v0, but if we'll add weapons in step 4 we might as well leave rotation free now and accept the visual ball-spin (mostly invisible since the slight_smile sprite is roughly symmetric, but the squash/stretch on wall hits would look weird if the ball is rotating).

Want me to proceed with step 1 (bare scaffold) as the next concrete deliverable? I'll show the new main.lua for review before saving it.

  1. 480x270, 2. Copy Emoji Ball Battles here. You may proceed with step 1.

Bash (grep -n "^function|make_entity|process_destroy_queue|collection_update|sync_...)

23:      sync_engine_globals()          -- refresh time/frame/etc. mirrors
26:      process_destroy_queue()        -- drain deferred destruction
45:    - class(), make_entity(), process_destroy_queue()
46:    - collection_update()  (see anchor/helpers.lua)
88:  sync_engine_globals()
101:function sync_engine_globals()
118:function set_time_scale(s)
152:  -- Set up dynamic global state (initial values; refreshed by sync_engine_globals)

Bash (grep -n "^function|^make_entity|^process_destroy_queue|^collection_update" E:...)

E:/a327ex/emoji-ball-bounce/anchor/object.lua:74:function make_entity(e)
E:/a327ex/emoji-ball-bounce/anchor/object.lua:87:function entity_kill(e)
E:/a327ex/emoji-ball-bounce/anchor/object.lua:97:function process_destroy_queue()
E:/a327ex/emoji-ball-bounce/anchor/helpers.lua:10:function collection_update(list, dt, method)

Drafting step 1: bare scaffold. Here's the full proposed main.lua for review before I save it. ~140 lines, drops the projectile/VFX/chamber, keeps the same render pipeline and conventions as the reference scaffold so step 2's energy systems and step 3's spawn keys slot in cleanly.

--[[
  Emoji Ball Bounce — Anchor 2.

  v0 step 1: bare physics scaffold.

  Open arena ported from Emoji Ball Battles: 480x270 viewport at scale 3,
  200x200 play area centered, four static rectangle walls wrapped around
  the interior (each WALL_THICKNESS thick, sized so adjacent walls overlap
  and seal the corners). One ball at center, EBB physics (restitution 1,
  no friction, no damping, gravity_scale 1, CCD bullet). No energy systems
  yet — Box2D will leak energy and the ball will gradually slow. Step 2
  will add EBB's six-system energy fix; step 3 adds multi-ball spawn keys.

  Render pipeline (mirrors reference/main.lua, simplified — no effects
  layer in v0 since there are no projectiles or particles):
    1. queue draws into game_layer (and bg/ui)
    2. layer_render(...) flushes queued commands to each layer's FBO
    3. derive shadow_layer := game_layer + shadow shader
       derive game_outline := game_layer + outline shader
    4. composite: bg -> shadow (offset +4,+4) -> outline -> game -> ui
]]

require('anchor')({
  width  = 480,
  height = 270,
  title  = 'Emoji Ball Bounce',
  scale  = 3,
  filter = 'rough',
})

gw, gh = width, height

-- -----------------------------------------------------------------------------
-- palette (Twitter emoji / Emoji Ball Battles)
-- -----------------------------------------------------------------------------
white      = color(255, 255, 255)
black      = color(0, 0, 0)
fg         = color(231, 232, 233)
yellow     = color(253, 205, 86)
wall_color = color_mix(fg, yellow, 0.1)

sky_top    = color(135, 206, 235)
sky_bottom = color(231, 232, 233)

-- -----------------------------------------------------------------------------
-- constants
-- -----------------------------------------------------------------------------
ARENA_W, ARENA_H = 200, 200
ARENA_CX, ARENA_CY = gw/2, gh/2
WALL_THICKNESS  = 200            -- EBB-faithful; large enough that corners overlap and no projectile / ball can squeeze past

BALL_RADIUS = 10
BALL_SPEED  = 240                 -- initial launch speed; gravity takes over from there

WORLD_GRAVITY_Y = 384             -- matches EBB

-- -----------------------------------------------------------------------------
-- physics
-- -----------------------------------------------------------------------------
physics_init()
physics_set_gravity(0, WORLD_GRAVITY_Y)
physics_register_tag('ball')
physics_register_tag('wall')
physics_enable_collision('ball', 'wall')

-- -----------------------------------------------------------------------------
-- layers
-- -----------------------------------------------------------------------------
bg_layer     = layer_new('bg')
game_layer   = layer_new('game')
shadow_layer = layer_new('shadow')
game_outline = layer_new('game_outline')
ui_layer     = layer_new('ui')

-- -----------------------------------------------------------------------------
-- shaders
-- -----------------------------------------------------------------------------
shadow_shader  = shader_load_file('assets/shadow.frag')
outline_shader = shader_load_file('assets/outline.frag')
shader_set_vec2_immediate(outline_shader, 'u_pixel_size', 1/gw, 1/gh)

-- -----------------------------------------------------------------------------
-- images
-- -----------------------------------------------------------------------------
slight_smile = image_load('slight_smile', 'assets/slight_smile.png')

-- -----------------------------------------------------------------------------
-- camera
-- -----------------------------------------------------------------------------
main_camera = camera_new(gw, gh)
shake_handcam(main_camera.shake, true, { x = 2, y = 2, rotation = 0.02 }, 0.5)

-- -----------------------------------------------------------------------------
-- entity collections
-- -----------------------------------------------------------------------------
balls = {}

-- =============================================================================
-- wall — static rectangular collider, drawn as a plain wall_color rectangle.
-- Walls extend WALL_THICKNESS past the arena interior in their outer
-- direction so adjacent walls overlap and the corner squares are filled.
-- The inner edge is what frames the play area; the outer portions get
-- naturally clipped by the framebuffer at the screen edge.
-- =============================================================================
wall = class()

function wall:new(x, y, w, h)
  self.x, self.y = x, y
  self.w, self.h = w, h
  make_entity(self)
  self.collider = collider(self, 'wall', 'static', 'box', w, h)
  self.collider:set_position(x, y)
  self.collider:set_restitution(1)
  self.collider:set_friction(0)
end

function wall:draw()
  layer_rectangle(game_layer, self.x - self.w/2, self.y - self.h/2, self.w, self.h, wall_color())
end

function wall:destroy()
  if self.collider then self.collider:destroy() end
end

-- =============================================================================
-- ball — slight_smile emoji bouncing under gravity. EBB-faithful: restitution
-- 1, friction 0, no linear damping, gravity_scale 1, CCD bullet so it can't
-- tunnel through walls at high speed. Rotation is NOT fixed — matches EBB
-- (free spin from collision moments).
-- =============================================================================
ball = class()

function ball:new(x, y)
  self.x, self.y = x, y
  self.radius    = BALL_RADIUS
  make_entity(self)
  self.spring = spring_new()
  spring_add(self.spring, 'hit', 1)

  self.collider = collider(self, 'ball', 'dynamic', 'circle', self.radius)
  self.collider:set_position(x, y)
  self.collider:set_restitution(1)
  self.collider:set_friction(0)
  self.collider:set_linear_damping(0)
  self.collider:set_gravity_scale(1)
  self.collider:set_bullet(true)

  local a = random_float(0, 2*math.pi)
  self.collider:set_velocity(BALL_SPEED * math.cos(a), BALL_SPEED * math.sin(a))

  self.image       = slight_smile
  self.image_scale = 2 * self.radius / self.image.width
end

function ball:on_wall_hit(hx, hy, nx, ny)
  spring_pull(self.spring, 'hit', 0.3)
end

function ball:update(dt)
  spring_update(self.spring, dt)
  self.collider:sync()
end

function ball:draw()
  local s = self.spring.hit.x
  local scale = self.image_scale * s
  layer_push(game_layer, self.x, self.y, self.collider:get_angle(), scale, scale)
  layer_image(game_layer, self.image, 0, 0)
  layer_pop(game_layer)
end

function ball:destroy()
  if self.collider then self.collider:destroy() end
end

-- -----------------------------------------------------------------------------
-- spawn helpers
-- -----------------------------------------------------------------------------
function spawn_ball(x, y)
  local b = ball(x, y)
  balls[#balls + 1] = b
  return b
end

-- -----------------------------------------------------------------------------
-- init
-- -----------------------------------------------------------------------------
local hw, hh, t = ARENA_W/2, ARENA_H/2, WALL_THICKNESS
top_wall    = wall(ARENA_CX,           ARENA_CY - hh - t/2, ARENA_W + 2*t, t)
bottom_wall = wall(ARENA_CX,           ARENA_CY + hh + t/2, ARENA_W + 2*t, t)
left_wall   = wall(ARENA_CX - hw - t/2, ARENA_CY,           t,            ARENA_H + 2*t)
right_wall  = wall(ARENA_CX + hw + t/2, ARENA_CY,           t,            ARENA_H + 2*t)

spawn_ball(ARENA_CX, ARENA_CY)

-- -----------------------------------------------------------------------------
-- main loop
-- -----------------------------------------------------------------------------
function update(dt)
  sync_engine_globals()
  collection_update(balls, dt)

  for _, ev in ipairs(collision_entities_begin('ball', 'wall')) do
    local b = ev.a
    if b and not b._dead then
      b:on_wall_hit(ev.x or b.x, ev.y or b.y, ev.nx or 0, ev.ny or 0)
    end
  end

  camera_update(main_camera, dt)
  process_destroy_queue()
end

function draw()
  layer_rectangle_gradient_v(bg_layer, 0, 0, gw, gh, sky_top(), sky_bottom())

  camera_attach(main_camera, game_layer)
  top_wall:draw(); bottom_wall:draw(); left_wall:draw(); right_wall:draw()
  for _, b in ipairs(balls) do b:draw() end
  camera_detach(main_camera, game_layer)

  layer_render(bg_layer)
  layer_render(game_layer)
  layer_render(ui_layer)

  layer_clear(shadow_layer)
  layer_draw_from(shadow_layer, game_layer, shadow_shader)

  layer_clear(game_outline)
  layer_draw_from(game_outline, game_layer, outline_shader)

  layer_draw(bg_layer)
  layer_draw(shadow_layer, 4, 4)
  layer_draw(game_outline)
  layer_draw(game_layer)
  layer_draw(ui_layer)
end

A few things I want to flag honestly:

  1. The walls use plain layer_rectangle (no rounded corners). EBB does the same — its walls are sharp rectangles, the visual softness comes from the outline shader. The reference scaffold's chamber used layer_rounded_rectangle. I'm matching EBB.
  2. Ball rotation is free. Per your "copy EBB" answer. The slight_smile face will visibly tilt as the ball spins from collision moments. This looks slightly chaotic for a face emoji (vs. an abstract circle) — push back if it bugs you and we'll add set_fixed_rotation(true).
  3. No :on_wall_hit energy logic, no per-frame max-speed cap. Step 2 work. Step 1 is meant to bleed energy as a baseline so step 2's effect is observable.
  4. No SFX yet — the ball_wall.ogg and concrete_*.ogg files are sitting in assets/ but I'm not playing them in v0. Easy to add when we want polish.

Does this look right? If yes, I'll save it to emoji-ball-bounce/main.lua.

Yes.

Write (E:/a327ex/emoji-ball-bounce/main.lua)

File created successfully at: E:/a327ex/emoji-ball-bounce/main.lua (file state is current in your context — no need to Read it back)

Saved to main.lua. Run run.bat from the project root — you should see one slight_smile emoji bouncing inside a 200×200 off-white-framed arena, gradually slowing as Box2D bleeds energy.

When you've confirmed the baseline works (or surfaced anything wrong with the layout, walls, or ball physics), let me know and I'll proceed to step 2: the six energy systems.

Yea, it works, you may proceed.

Before I write, let me verify a couple of helpers exist in the engine. EBB uses an.random:bool(percent) and an.random:sign() — I want to confirm the equivalent globals exist in Anchor 2.

Grep (l_random_bool|l_random_sign|random_bool|random_sign)

7550:// random_sign(chance?, rng?) - Returns -1 or 1 (chance 0-100, default 50)
7551:static int l_random_sign(lua_State* L) {
7569:// random_bool(chance?, rng?) - Returns true or false (chance 0-100, default 50)
7570:static int l_random_bool(lua_State* L) {
8970:    lua_register(L, "random_sign", l_random_sign);
8971:    lua_register(L, "random_bool", l_random_bool);

Read (E:/a327ex/emoji-ball-bounce/anchor/init.lua)

1    --[[
2     Anchor 2 — framework initialization.
3   
4     Loads all framework modules in dependency order, then returns a function
5     that takes config and initializes the engine + global state. The game's
6     main.lua is expected to define `update(dt)` and `draw()` as globals; the
7     C engine calls these directly each frame.
8   
9     Usage (from a game's main.lua):
10      require('anchor')({
11        width = 480,
12        height = 270,
13        title = "My Game",
14        scale = 3,
15        vsync = true,
16        filter = "rough",
17        -- render_uncapped = true,   -- opt out of the 60Hz render cap; let
18                                     -- vsync pace render. Use for non-pixel-
19                                     -- art games where the cap shows judder.
20      })
21  
22      function update(dt)
23        sync_engine_globals()          -- refresh time/frame/etc. mirrors
24        -- your game update (physics is stepped by the engine automatically
25        -- before update() is called; you just consume collision events here)
26        process_destroy_queue()        -- drain deferred destruction
27      end
28  
29      function draw()
30        -- ... your game draw
... [80 more lines]

Grep (self.radius\s=\s\d)

1775:  self.radius = 10

Step 2: the six energy systems

Here are the proposed changes. I'll group them by what's new vs. modified so you can scan them.

New constants — add after WORLD_GRAVITY_Y:

-- -----------------------------------------------------------------------------
-- energy system constants (EBB-faithful; see arena_energy block below for design)
-- -----------------------------------------------------------------------------
MAX_BALL_SPEED        = 448
BALL_ENERGY_BOOST     = 1.09
MIN_WALL_ENERGY_BOOST = 1.0    -- at high system_energy (>=400)
MAX_WALL_ENERGY_BOOST = 1.11   -- at low system_energy (<=250)

ARENA_FLOOR_Y = ARENA_CY + ARENA_H/2   -- inner floor y, used by stuck-ball detection

Add ball-ball collision pair — in the physics section:

physics_enable_collision('ball', 'wall')
physics_enable_collision('ball', 'ball')   -- NEW

New energy state + per-frame update — replace the balls = {} line with:

balls = {}

--[[
  arena energy — six-system port from Emoji Ball Battles. Box2D leaks energy
  even at restitution=1; without compensation the ball gradually settles into
  a low-energy oscillation. EBB layers six systems on top of restitution-1
  collisions to keep the system at a stable equilibrium AND inject pacing
  variety. We port all six (skipping system 7, weapon-weapon, until weapons
  exist):

    1. ball energy boost (1.09x)        — every ball-ball collision
    2. wall energy boost (<=1.11x)      — ball-wall, probabilistic
    3. energy redistribution            — ball-ball, probabilistic
    4. high-speed bypass (lose 30%)     — ball-ball, S-curve probability
    5. low-horizontal kick              — ball-ball, linear probability
    6. stuck-ball hop                   — per-ball update (in ball:update)

  EBB-faithful with one fix: system_energy is the sum of live ball speeds
  refreshed each frame (EBB only updates it on ball-ball collisions, which
  is silent for a single ball). Without this fix wall_boost_chance/value
  stay frozen at the initial state forever in single-ball configurations.
]]
arena_energy = {
  system_energy            = 250,    -- sum of all live ball speeds (refreshed each frame)
  wall_energy_boost        = 1.0,    -- magnitude applied on ball-wall hits when chance triggers
  wall_boost_chance        = 0,      -- 0-100 probability for system 2
  high_speed_hit_count     = 0,      -- consecutive ball-ball hits where max_speed > 0.78*MAX
  low_horizontal_hit_count = 0,      -- consecutive ball-ball hits where |vx_a|+|vx_b| < 0.25*MAX
}

function arena_energy_update()
  local total = 0
  for _, b in ipairs(balls) do
    if not b._dead then
      local vx, vy = b.collider:get_velocity()
      total = total + math.length(vx, vy)
    end
  end
  arena_energy.system_energy = total

  local energy_ratio = math.remap(math.clamp(total, 100, 600), 100, 600, 0, 1)
  arena_energy.wall_boost_chance = (1 - math.quad_out(energy_ratio)) * 100

  if total <= 250 then
    arena_energy.wall_energy_boost = MAX_WALL_ENERGY_BOOST
  elseif total >= 400 then
    arena_energy.wall_energy_boost = MIN_WALL_ENERGY_BOOST
  else
    local boost_ratio = math.remap(total, 250, 400, 0, 1)
    arena_energy.wall_energy_boost = math.lerp(math.sine_out(boost_ratio), MAX_WALL_ENERGY_BOOST, MIN_WALL_ENERGY_BOOST)
  end
end

Modified ball:new — add low_vy state init at the bottom:

  -- ... existing ball setup ...
  self.image       = slight_smile
  self.image_scale = 2 * self.radius / self.image.width

  -- Stuck-ball state (system 6). Threshold is re-rolled on each trigger so
  -- the hop cadence isn't perfectly regular when the ball lingers near the floor.
  self.low_vy_time      = 0
  self.low_vy_threshold = random_float(0.5, 1.5)
end

Modified ball:update — add stuck-ball detection:

function ball:update(dt)
  spring_update(self.spring, dt)
  self.collider:sync()

  -- System 6: stuck-ball detection. While the ball lingers near the floor
  -- with near-zero vertical velocity, accumulate time; once it exceeds the
  -- threshold, apply an unstick impulse (small horizontal nudge in the
  -- direction of current vx, plus a strong upward kick).
  local vx, vy = self.collider:get_velocity()
  local near_floor = self.y + self.radius > ARENA_FLOOR_Y - 20
  if near_floor then
    self.low_vy_time = self.low_vy_time + dt
    if self.low_vy_time > self.low_vy_threshold and math.abs(vy) < 15 then
      self.low_vy_time      = 0
      self.low_vy_threshold = random_float(0.5, 1.5)
      self.collider:apply_impulse(math.sign(vx) * random_float(0, 6), -24)
    end
  else
    self.low_vy_time = 0
  end
end

Modified update(dt) — replace the existing one:

function update(dt)
  sync_engine_globals()
  collection_update(balls, dt)

  -- Refresh system_energy from live ball speeds. Must run BEFORE the
  -- ball-wall drain so wall_boost_chance / wall_energy_boost are current.
  arena_energy_update()

  -- Ball-ball: systems 1, 3, 4, 5 + speed cap.
  for _, ev in ipairs(collision_entities_begin('ball', 'ball')) do
    local a, b = ev.a, ev.b
    if a and b and not a._dead and not b._dead then
      local vx_a, vy_a = a.collider:get_velocity()
      local vx_b, vy_b = b.collider:get_velocity()
      local speed_a = math.length(vx_a, vy_a)
      local speed_b = math.length(vx_b, vy_b)
      local max_speed = math.max(speed_a, speed_b)

      -- System 4: high-speed bypass (S-curve probability, guaranteed at 9 hits).
      -- When triggered, both balls lose 30% energy — a deliberate calm beat.
      if max_speed > 0.78 * MAX_BALL_SPEED then
        arena_energy.high_speed_hit_count = arena_energy.high_speed_hit_count + 1
      end
      local normalized = math.clamp(arena_energy.high_speed_hit_count, 0, 9) / 9
      local bypass = random_bool(math.cubic_in_out(normalized) * 100)

      if bypass then
        arena_energy.high_speed_hit_count = 0
        local k = 0.7
        vx_a, vy_a = vx_a*k, vy_a*k
        vx_b, vy_b = vx_b*k, vy_b*k
      else
        -- System 3: energy redistribution. Probability scales with max_speed.
        -- Picks a random target ratio from N(0.5, stddev), blends current ratio
        -- toward it. stddev shrinks 0.3 -> 0.1 with speed (tighter at high speed).
        local speed_ratio = math.remap(max_speed, 0, MAX_BALL_SPEED, 0, 1)
        if random_bool(speed_ratio * 100) then
          local energy_a = vx_a*vx_a + vy_a*vy_a
          local energy_b = vx_b*vx_b + vy_b*vy_b
          local total_energy = energy_a + energy_b
          if total_energy > 0 and energy_a > 0.01 and energy_b > 0.01 then
            local ratio_a    = energy_a / total_energy
            local stddev     = math.remap(speed_ratio, 0, 1, 0.3, 0.1)
            local target_a   = random_normal(0.5, stddev)
            local new_ratio_a = math.clamp(math.lerp(speed_ratio, ratio_a, target_a), 0.05, 0.95)
            local scale_a = math.sqrt((total_energy * new_ratio_a)       / energy_a)
            local scale_b = math.sqrt((total_energy * (1 - new_ratio_a)) / energy_b)
            vx_a, vy_a = vx_a*scale_a, vy_a*scale_a
            vx_b, vy_b = vx_b*scale_b, vy_b*scale_b
          end
        end
      end

      -- System 1: per-collision energy boost (compensates Box2D leakage). Skip
      -- on bypass (the bypass deliberately drained energy; boosting back undoes it).
      if not bypass then
        vx_a, vy_a = vx_a*BALL_ENERGY_BOOST, vy_a*BALL_ENERGY_BOOST
        vx_b, vy_b = vx_b*BALL_ENERGY_BOOST, vy_b*BALL_ENERGY_BOOST
      end

      -- Cap speed at MAX_BALL_SPEED (preserves direction).
      local s_a = math.length(vx_a, vy_a)
      if s_a > MAX_BALL_SPEED then local k = MAX_BALL_SPEED/s_a; vx_a, vy_a = vx_a*k, vy_a*k end
      local s_b = math.length(vx_b, vy_b)
      if s_b > MAX_BALL_SPEED then local k = MAX_BALL_SPEED/s_b; vx_b, vy_b = vx_b*k, vy_b*k end

      -- System 5: low-horizontal kick. Counts consecutive collisions where total
      -- horizontal energy is low; chance ramps linearly to 100% at 4 hits.
      if math.abs(vx_a) + math.abs(vx_b) < 0.25 * MAX_BALL_SPEED then
        arena_energy.low_horizontal_hit_count = arena_energy.low_horizontal_hit_count + 1
        local kick_chance = math.clamp(arena_energy.low_horizontal_hit_count, 0, 4) / 4
        if random_bool(kick_chance * 100) then
          arena_energy.low_horizontal_hit_count = 0
          vx_a = random_sign() * random_float(100, 200)
          vx_b = random_sign() * random_float(100, 200)
        end
      else
        arena_energy.low_horizontal_hit_count = 0
      end

      a.collider:set_velocity(vx_a, vy_a)
      b.collider:set_velocity(vx_b, vy_b)
    end
  end

  -- Ball-wall: system 2 (wall energy boost), then ball spring pull.
  for _, ev in ipairs(collision_entities_begin('ball', 'wall')) do
    local b = ev.a
    if b and not b._dead then
      local vx, vy = b.collider:get_velocity()
      if random_bool(arena_energy.wall_boost_chance) and arena_energy.wall_energy_boost > 1 then
        b.collider:set_velocity(vx * arena_energy.wall_energy_boost, vy * arena_energy.wall_energy_boost)
      end
      b:on_wall_hit(ev.x or b.x, ev.y or b.y, ev.nx or 0, ev.ny or 0)
    end
  end

  camera_update(main_camera, dt)
  process_destroy_queue()
end

A few honest notes

  1. Single-ball test: with one ball, only systems 2 and 6 fire. Expected behavior: ball settles into a steady-state bounce pattern, never stalls. If it accelerates without bound or drifts to a slow stall, system 2's tuning (the energy curve thresholds 100/250/400/600) needs adjustment — these were tuned for two-ball EBB and the single-ball steady-state energy is a different number. I'm porting the constants verbatim and we'll see if they hold.
  2. Multi-ball is the EBB-tested configuration. When you spawn 2+ balls in step 3, the full system kicks in and behavior should match EBB closely.
  3. No ball-ball collision drain side-effects yet: no SFX, no spring pull on ball-ball, no hit VFX. Step 3 (or a polish step) can add those.
  4. b:on_wall_hit still does just the hit-spring pull. No SFX, no squash. Same reason — polish later.

Look right? If yes I'll save it.

Let's only add the system that fires when we have a single ball. Then when we add more balls we'll add the other systems. We need to make sure it works the same with all possible configurations, and the original system assumed there would always be 2 balls and no more or less.

Right, that's the smarter scope. Let me cut systems 1, 3, 4, 5 from step 2 entirely.

For step 2: only systems 2 (wall energy boost) and 6 (stuck-ball hop). Both operate on individual balls, so they generalize correctly to any ball count. The four ball-ball systems land in step 3 alongside multi-ball spawn, where we can also reason about >2 balls (EBB never tested 3+ — the global counters in systems 4 and 5 would tick faster with more pairs and likely need tuning).

Revised step 2 changes:

New constants — add after WORLD_GRAVITY_Y:

-- -----------------------------------------------------------------------------
-- energy system constants (EBB-faithful; see arena_energy block below)
-- -----------------------------------------------------------------------------
MAX_BALL_SPEED        = 448
MIN_WALL_ENERGY_BOOST = 1.0    -- at high system_energy (>=400)
MAX_WALL_ENERGY_BOOST = 1.11   -- at low system_energy (<=250)

ARENA_FLOOR_Y = ARENA_CY + ARENA_H/2   -- inner floor y, used by stuck-ball detection

New energy state + per-frame update — replace the balls = {} line with:

balls = {}

--[[
  arena energy — port of the single-ball-relevant subset of EBB's collision
  energy system. Box2D leaks energy even at restitution=1; without
  compensation a ball gradually settles into a low-energy oscillation. EBB
  layers six systems on top to keep a stable equilibrium and inject pacing
  variety. Only two of those six fire for a single ball:

    - system 2: wall energy boost. On ball-wall collisions, probabilistically
      multiply the ball's velocity by a small factor. Chance and magnitude
      are both shaped by system_energy (sum of all live ball speeds): high
      chance + max boost when energy is low, fading out as energy rises.
    - system 6: stuck-ball hop (in ball:update). When a ball lingers near
      the floor with near-zero vertical velocity, kick it upward.

  EBB-faithful with one fix: system_energy is refreshed each frame from
  current ball speeds. EBB only updates it on ball-ball collisions, so for
  a single ball it would stay frozen at the initial 250 forever.

  The ball-ball systems (1, 3, 4, 5) land in step 3 with multi-ball spawn.
]]
arena_energy = {
  system_energy     = 250,    -- sum of all live ball speeds (refreshed each frame)
  wall_energy_boost = 1.0,    -- magnitude applied when chance triggers
  wall_boost_chance = 0,      -- 0-100 probability per ball-wall collision
}

function arena_energy_update()
  local total = 0
  for _, b in ipairs(balls) do
    if not b._dead then
      local vx, vy = b.collider:get_velocity()
      total = total + math.length(vx, vy)
    end
  end
  arena_energy.system_energy = total

  local energy_ratio = math.remap(math.clamp(total, 100, 600), 100, 600, 0, 1)
  arena_energy.wall_boost_chance = (1 - math.quad_out(energy_ratio)) * 100

  if total <= 250 then
    arena_energy.wall_energy_boost = MAX_WALL_ENERGY_BOOST
  elseif total >= 400 then
    arena_energy.wall_energy_boost = MIN_WALL_ENERGY_BOOST
  else
    local boost_ratio = math.remap(total, 250, 400, 0, 1)
    arena_energy.wall_energy_boost = math.lerp(math.sine_out(boost_ratio), MAX_WALL_ENERGY_BOOST, MIN_WALL_ENERGY_BOOST)
  end
end

Modified ball:new — add stuck-ball state at the bottom:

  -- ... existing setup ...
  self.image       = slight_smile
  self.image_scale = 2 * self.radius / self.image.width

  -- Stuck-ball state (system 6). Threshold re-rolled on each trigger so
  -- the hop cadence isn't perfectly regular when the ball lingers near the floor.
  self.low_vy_time      = 0
  self.low_vy_threshold = random_float(0.5, 1.5)
end

Modified ball:update — add stuck-ball detection:

function ball:update(dt)
  spring_update(self.spring, dt)
  self.collider:sync()

  -- System 6: stuck-ball hop. While the ball is near the floor with near-
  -- zero vertical velocity, accumulate time. Once it exceeds the threshold,
  -- apply a small horizontal nudge in the direction of vx plus a strong
  -- upward kick. Threshold and impulse magnitudes are EBB-faithful.
  local vx, vy = self.collider:get_velocity()
  local near_floor = self.y + self.radius > ARENA_FLOOR_Y - 20
  if near_floor then
    self.low_vy_time = self.low_vy_time + dt
    if self.low_vy_time > self.low_vy_threshold and math.abs(vy) < 15 then
      self.low_vy_time      = 0
      self.low_vy_threshold = random_float(0.5, 1.5)
      self.collider:apply_impulse(math.sign(vx) * random_float(0, 6), -24)
    end
  else
    self.low_vy_time = 0
  end
end

Modified update(dt) — add arena_energy_update call + system 2 in ball-wall drain:

function update(dt)
  sync_engine_globals()
  collection_update(balls, dt)

  -- Refresh system_energy from live ball speeds. Must run BEFORE the
  -- ball-wall drain so wall_boost_chance / wall_energy_boost are current.
  arena_energy_update()

  for _, ev in ipairs(collision_entities_begin('ball', 'wall')) do
    local b = ev.a
    if b and not b._dead then
      -- System 2: probabilistic wall energy boost.
      local vx, vy = b.collider:get_velocity()
      if random_bool(arena_energy.wall_boost_chance) and arena_energy.wall_energy_boost > 1 then
        b.collider:set_velocity(vx * arena_energy.wall_energy_boost, vy * arena_energy.wall_energy_boost)
      end
      b:on_wall_hit(ev.x or b.x, ev.y or b.y, ev.nx or 0, ev.ny or 0)
    end
  end

  camera_update(main_camera, dt)
  process_destroy_queue()
end

Honest expectations

Look right? I'll save it once you confirm.

Looks great, additionally draw text system energy somewhere on the screen so I can see the value.

Need to set up text rendering — let me check what's available.

Bash (grep -n "^function|^font\b" E:/a327ex/emoji-ball-bounce/anchor/font.lua 2>&1 | ...)

12:font = class()
18:function font:new(name, path, size, filter)
26:function font:text_width(text)
30:function font:char_width(codepoint)
34:function font:glyph_metrics(codepoint)
39:function font_register(name, path, size, filter)
---
E:/a327ex/emoji-ball-bounce/anchor/font.lua:6:    layer_text(game_layer, "Hello", fonts.main, 100, 50, color)
E:/a327ex/emoji-ball-bounce/anchor/font.lua:22:  font_load(name, path, size, filter)
E:/a327ex/emoji-ball-bounce/anchor/layer.lua:174:function layer_texture(lyr, tex, x, y, color)
E:/a327ex/emoji-ball-bounce/anchor/layer.lua:193:function layer_text(lyr, text, f, x, y, color)
E:/a327ex/emoji-ball-bounce/anchor/memory.lua:182:  layer_text(layer, 'MEMORY (F3 hide / F4 baseline)', font, x, y, header_color)
E:/a327ex/emoji-ball-bounce/anchor/memory.lua:185:    layer_text(layer, 'baseline captured', font, x, y, header_color)
E:/a327ex/emoji-ball-bounce/anchor/memory.lua:187:    layer_text(layer, 'no baseline yet', font, x, y, header_color)
E:/a327ex/emoji-ball-bounce/anchor/memory.lua:199:    layer_text(layer, label, font, x, y, text_color)
E:/a327ex/emoji-ball-bounce/anchor/memory.lua:200:    layer_text(layer, fmt_value(cur, kind), font, x + col_label_w, y, text_color)
E:/a327ex/emoji-ball-bounce/anchor/memory.lua:202:      layer_text(layer, fmt_delta(delta, kind), font, x + col_label_w + col_value_w, y, delta_color)

Bash (ls E:/a327ex/emoji-ball-bounce/assets/.ttf E:/a327ex/emoji-ball-bounce/assets/...)

ls: cannot access 'E:/a327ex/emoji-ball-bounce/assets/*.ttf': No such file or directory
ls: cannot access 'E:/a327ex/emoji-ball-bounce/assets/*.otf': No such file or directory
---
ls: cannot access 'E:/a327ex/emoji-ball-battles/assets/*.otf': No such file or directory
E:/a327ex/emoji-ball-battles/assets/FatPixelFont.ttf
E:/a327ex/emoji-ball-battles/assets/LanaPixel.ttf

Read (E:/a327ex/emoji-ball-bounce/anchor/font.lua)

1    --[[
2     font — thin wrapper over C font functions.
3   
4     Usage:
5       fonts.main = font_register('main', 'assets/LanaPixel.ttf', 11)
6       layer_text(game_layer, "Hello", fonts.main, 100, 50, color)
7   
8     A font is a plain table with .name, .size, .height plus query methods.
9     Stays as a simple class/struct pattern for consistent access.
10  ]]
11  
12  font = class()
13  
14  --- `filter` is optional: 'smooth' (grayscale atlas + linear sampling) or
15  --- 'rough' (1-bit mono atlas + nearest sampling). Defaults to the engine's
16  --- current global filter mode. The filter is baked into the atlas at load time
17  --- and cannot be changed afterward — load two copies if you need both.
18  function font:new(name, path, size, filter)
19    self.name = name
20    self.size = size
21    self.filter = filter
22    font_load(name, path, size, filter)
23    self.height = font_get_height(name)
24  end
25  
26  function font:text_width(text)
27    return font_get_text_width(self.name, text)
28  end
29  
30  function font:char_width(codepoint)
... [14 more lines]

Read (E:/a327ex/emoji-ball-bounce/anchor/layer.lua)

188      color or 0xFFFFFFFF,
189     flash or 0
190   )
191 end
192 
193 function layer_text(lyr, text, f, x, y, color)
194   local font_name = type(f) == 'string' and f or f.name
195   eng.draw_text(lyr_handle(lyr), text, font_name, x, y, color)
196 end
197 
198 function layer_push(lyr, x, y, r, sx, sy)
199   eng.push(lyr_handle(lyr), x, y, r, sx, sy)
200 end
201 
202 function layer_pop(lyr)

Two extra additions on top of the energy systems:

Font asset — copy LanaPixel.ttf from EBB (no fonts in this project yet, that's the cleanest pixel font in the EBB set).

Font register — add after slight_smile:

font_register('main', 'assets/LanaPixel.ttf', 11)

Debug text in draw — add at the top of draw() alongside the bg gradient queue:

layer_text(ui_layer, string.format('energy: %.0f', arena_energy.system_energy), fonts.main, 4, 4, black())

Top-left, black for contrast against the sky gradient. No outline/shadow (UI layer skips both — clean flat text). Easy to remove later.

Saving everything now.

Bash (cp E:/a327ex/emoji-ball-battles/assets/LanaPixel.ttf E:/a327ex/emoji-ball-bounce...)

-rw-r--r-- 1 adn 197121 3154436 Apr 27 10:00 E:/a327ex/emoji-ball-bounce/assets/LanaPixel.ttf

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All saved. Run it and watch the energy readout — single ball should hold a stable equilibrium somewhere in the 100–250 range without stalling. If it pins at MAX (448) or trends to 0 over a minute, we tune the curve. If it gets stuck on the floor, system 6 should hop it within 0.5–1.5 s.

When you're satisfied with single-ball stability, let me know and we'll proceed to step 3: multi-ball spawn keys + the four ball-ball energy systems.

Let's add another system first. Keep track of the ratio between horizontal and vertical velocity. A single ball has a tendency towards horizontal velocity. The more the ratio favors horizontal velocity, the higher the probability that the next time it hits the ground, it will be kicked upwards with higher velocity, kinda like the system 6 kick. First, let's do the ratio first so I can see what the numbers look like in reality. Draw the 3 values (horizontal velocity, vertical velocity, ratio) below the energy.

Quick design choice on the ratio definition before I write — there are two natural forms:

I'll go with the bounded form since the eventual kick threshold is easier to reason about ("kick when ratio > 0.8"), and the divergence in the literal form would be visually distracting in the readout. Push back if you want the unbounded one — we can switch trivially.

For the display I'll show |vx| and |vy| (magnitudes, not signed) since direction doesn't matter for the question being asked.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Saved. Y-positions are 4 / 16 / 28 / 40 — 12px line spacing for the size-11 LanaPixel.

Run and watch the values. What I'd expect:

When you're ready to design the kick logic, tell me what threshold and what kick magnitude/probability shape you want — or feel free to just describe the gameplay feel you want and I'll propose constants.

The ratio doesn't quite work because vy keeps changing too much. I think the more correct one would be the last highest y the ball reached. The longer it hasn't been above half the height of the arena, the higher the chance of a kick.

Good call — vy crosses zero at every apex so the ratio is junk. Time-below-half-height is much cleaner: it's monotonic over a flat-bouncing regime, resets cleanly when the ball arcs high again, and reads as a single intuitive seconds value.

Threshold: y < ARENA_CY (the arena's vertical midpoint). Reset to 0 when the ball is in the upper half, accumulate dt otherwise.

Three changes:

ball:new — add at the bottom alongside the stuck-ball state:

  -- Time the ball has spent in the lower half of the arena without crossing
  -- the midline. Used by the upcoming horizontal-bias kick: long stretches
  -- below the midline indicate a flat bouncing pattern that needs a vertical
  -- impulse to break.
  self.time_below_half = 0

ball:update — add after self.collider:sync():

  if self.y < ARENA_CY then
    self.time_below_half = 0
  else
    self.time_below_half = self.time_below_half + dt
  end

draw — replace the h / v / ratio readout block with:

  local b = balls[1]
  if b then
    layer_text(ui_layer, string.format('below half: %.2f s', b.time_below_half), fonts.main, 4, 16, black())
  end

Saving.

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Saved. Watch the below half value during play — it should oscillate between 0 (when the ball arcs up past the midline) and some peak just before it bounces high again.

When the bouncing pattern flattens out, the value should grow without resetting — that's the signal for the upcoming kick. Tell me the values you see (rough peaks during normal play vs. flat-bouncing) and we can pick a threshold + probability shape together.

As soon as it goes over 1s, start increasing the probability. It resets if it goes to 0 again. The probability curve should be similar to other curves that the system uses, your choice here, just tell me about it, ideally on a visual table with all probabilities over the curve.

Curve choice

I'd go with quad_in (f(t) = t²) over the range 1 s → 4 s. Rationale:

Roll cadence: chance is checked on each ball-floor contact (not per frame). That way the kick coincides with a bounce — visually it reads as "the ball hits the floor and unexpectedly bounces high," which is the intended effect.

Probability table

Formula: normalized = clamp((time_below_half - 1) / 3, 0, 1), then chance = quad_in(normalized) * 100.

time below half normalized quad_in(n) = n² chance per floor hit
≤ 1.0 s 0.00 0.000 0 %
1.25 s 0.083 0.007 0.7 %
1.50 s 0.167 0.028 2.8 %
1.75 s 0.250 0.063 6.3 %
2.00 s 0.333 0.111 11.1 %
2.25 s 0.417 0.174 17.4 %
2.50 s 0.500 0.250 25.0 %
2.75 s 0.583 0.340 34.0 %
3.00 s 0.667 0.444 44.4 %
3.25 s 0.750 0.563 56.3 %
3.50 s 0.833 0.694 69.4 %
3.75 s 0.917 0.840 84.0 %
≥ 4.00 s 1.00 1.000 100 %

A few alternatives if this doesn't fit

Pick one (or push the window wider/narrower) and I'll wire it in along with the floor-contact roll and the kick impulse design.

You can go with this, just to 8s instead of 4s. The kick should be gentler than the system 6 kick, and it should happen on the next time it hits the ground, not at any arbitrary time.

Locked-in numbers for 1–8 s quad_in:

time below half chance per floor hit
≤ 1.0 s 0%
2.0 s 2%
3.0 s 8%
4.0 s 18%
5.0 s 33%
6.0 s 51%
7.0 s 74%
≥ 8.0 s 100%

For "gentler than system 6" I'll go with ~2/3 magnitude: horizontal random_float(0, 4) (was 0–6) and vertical -16 (was -24). Direction still follows sign(vx). Push back if you want it gentler still (1/2 = 0, 3 and -12) or kept closer to system 6 (3/4 = 0, 4.5 and -18).

Floor detection: ev.ny > 0.5 (matches EBB's convention — contact normal points from ball into the wall, so a downward-facing normal means the wall is the floor below).

Two changes:

Add the kick to the ball-wall drain — modify the existing block:

for _, ev in ipairs(collision_entities_begin('ball', 'wall')) do
  local b = ev.a
  if b and not b._dead then
    -- System 2: probabilistic wall energy boost.
    local vx, vy = b.collider:get_velocity()
    if random_bool(arena_energy.wall_boost_chance) and arena_energy.wall_energy_boost > 1 then
      b.collider:set_velocity(vx * arena_energy.wall_energy_boost, vy * arena_energy.wall_energy_boost)
    end

    -- Horizontal-bias kick: when the ball has been below the midline too
    -- long (flat-bouncing failure mode), roll on each floor contact for an
    -- upward impulse. Threshold 1 s, guaranteed at 8 s, quad_in escalation.
    -- Gentler than system 6 since we're nudging a still-energetic ball, not
    -- unsticking a dead one.
    if (ev.ny or 0) > 0.5 and b.time_below_half > 1 then
      local n = math.clamp((b.time_below_half - 1) / 7, 0, 1)
      if random_bool(math.quad_in(n) * 100) then
        b.collider:apply_impulse(math.sign(vx) * random_float(0, 4), -16)
      end
    end

    b:on_wall_hit(ev.x or b.x, ev.y or b.y, ev.nx or 0, ev.ny or 0)
  end
end

Add the live kick-chance readout in draw — extend the debug block:

  local b = balls[1]
  if b then
    layer_text(ui_layer, string.format('below half: %.2f s', b.time_below_half), fonts.main, 4, 16, black())
    local n = math.clamp((b.time_below_half - 1) / 7, 0, 1)
    layer_text(ui_layer, string.format('kick chance: %.0f%%', math.quad_in(n) * 100), fonts.main, 4, 28, black())
  end

Note: a kick doesn't reset time_below_half directly — only the ball actually crossing the midline does. So if the kick is too gentle to clear half-height, the chance stays elevated and another kick rolls on the next floor hit. Multiple gentle kicks naturally stack until the ball escapes. Saving.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Saved. Watch the kick chance climb as the ball flat-bounces; the kick should land somewhere in the 3–6 s window most of the time, and the below half timer should snap back to 0 when the kick succeeds in clearing the midline.

Kick chance is 100% but the kick isn't actually happening.

Almost certainly the floor-detection condition is wrong. Let me check the actual collision-event convention in Anchor 2 — EBB uses a different framework so ev.ny > 0.5 is a guess.

Read (E:/a327ex/emoji-ball-bounce/anchor/physics.lua)

1    --[[
2     physics — entity-resolving wrappers for physics queries.
3   
4     The C engine's physics_query_* and physics_get_*_begin/end functions return
5     raw body handles with tag names. These framework helpers:
6       1. Resolve bodies to their owning entities via physics_get_user_data + entities
7       2. Normalize event ordering so `a` always corresponds to the first tag
8          argument in the query and `b` to the second
9   
10    The normalization matters because the engine's `tags_match` is order-
11    insensitive, so a query like `collision_entities_begin('player', 'enemy')`
12    could receive events where the collision was recorded as
13    `tag_a='enemy', tag_b='player'`. Without normalization, you'd get `ev.a`
14    being the enemy when you expected the player. These helpers check the
15    tag names and swap if needed so `ev.a` is always the first-tag entity.
16  
17    Usage:
18      for _, ev in ipairs(collision_entities_begin('player', 'enemy')) do
19        ev.a:hit(1)   -- always the player (first query tag)
20        -- ev.b        -- always the enemy (second query tag)
21      end
22  
23      for _, ev in ipairs(sensor_entities_begin('bullet', 'enemy')) do
24        ev.a:kill()   -- the bullet
25        ev.b:hit(1)   -- the enemy
26      end
27  ]]
28  
29  -- Internal: resolve a body handle to its owning entity via user_data.
30  local function body_to_entity(body)
... [225 more lines]

Grep (normal_x|normal_y|m_normal|GetWorldManifold|b2WorldManifold)

529:    float normal_x;     // Normal from A to B
530:    float normal_y;
553:    float normal_x;     // Normal from A to B
554:    float normal_y;
687:            ev->normal_x = contact_data.manifold.normal.x;
688:            ev->normal_y = contact_data.manifold.normal.y;
693:            ev->normal_x = 0;
694:            ev->normal_y = 0;
733:        ev->normal_x = e->normal.x;
734:        ev->normal_y = e->normal.y;
6687:// physics_get_collision_begin(tag_a, tag_b) -> array of {body_a, body_b, shape_a, shape_b, tag_a, tag_b, point_x, point_y, normal_x, normal_y}
6738:            lua_pushnumber(L, e->normal_x);
6739:            lua_setfield(L, -2, "normal_x");
6740:            lua_pushnumber(L, e->normal_y);
6741:            lua_setfield(L, -2, "normal_y");
6809:// physics_get_hit(tag_a, tag_b) -> array of {body_a, body_b, shape_a, shape_b, tag_a, tag_b, point_x, point_y, normal_x, normal_y, approach_speed}
6860:            lua_pushnumber(L, e->normal_x);
6861:            lua_setfield(L, -2, "normal_x");
6862:            lua_pushnumber(L, e->normal_y);
6863:            lua_setfield(L, -2, "normal_y");
7336:// physics_raycast(x1, y1, x2, y2, tags) -> {body, shape, point_x, point_y, normal_x, normal_y, fraction} or nil
7390:    lua_setfield(L, -2, "normal_x");
7392:    lua_setfield(L, -2, "normal_y");
7401:// physics_raycast_all(x1, y1, x2, y2, tags) -> array of {body, shape, point_x, point_y, normal_x, normal_y, fraction}
7450:        lua_setfield(L, -2, "normal_x");

[Showing results with pagination = limit: 25]

Found it. Looking at physics.lua:144-153, collision_entities_begin swaps body_a / body_b based on tag order, but does not flip the normal. The engine's normal points from "original body A to original body B" (from anchor.c:529-530) — and which body Box2D records as A vs. B is internal ordering, not user-controlled.

So ev.ny could be +1 or -1 for the same floor contact depending on which body Box2D happened to put first. That's why EBB's > 0.5 works there but is unreliable here.

The robust fix is position-based floor detection — the ball's bottom edge is at ARENA_FLOOR_Y exactly when it's touching the floor. Mirror what stuck-ball detection already does:

if b.y + b.radius >= ARENA_FLOOR_Y - 0.5 and b.time_below_half > 1 then

The - 0.5 is float-safety — Box2D's contact resolution may put the ball a tiny fraction inside the wall.

Saving.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Saved. Now floor hits should reliably trigger kick rolls.

This also raises an open issue I should flag: the same normal-direction unreliability will bite us again when we add ball-ball collisions in step 3 (the redistribution and bypass systems read collision normals indirectly via velocity, so they're fine, but anything that tries to use ev.nx/ev.ny directly will need the same position-based workaround). Worth fixing in the framework eventually — collision_entities_begin should flip the normal when it swaps bodies. But that's outside this session's scope unless you want to tackle it.

Just print ev.ny for me to see what it's usually at.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Saved. Output will go to stdout — visible in the console window if you're running from run.bat, or via wherever the engine pipes prints. Heads-up: floor bounces happen multiple times a second when the ball is in a flat trajectory, so expect spam. Tell me the values you see and we can decide whether the position-based floor check stays or goes.

When hitting the ground it's always -1

That reverses my earlier theory — I was wrong about the framework being unreliable. ev.ny is consistently -1 for floor in this engine, which means:

The framework normalization is fine — I owe you that correction. The convention in this engine is just: floor → ev.ny ≈ -1, ceiling → +1, left wall → ev.nx ≈ +1, right wall → -1 (always wall→ball).

What to do with this

The position-based check we have works and is robust to body-ordering surprises (e.g., if a ball ever happened to be created before some wall and the ordering flipped). The normal-based check is one line shorter and more idiomatic. Up to you:

Option A — leave position-based as is. Slightly more code but order-independent. The framework comment I left will rot since it's wrong, but the code works.

Option B — switch to ev.ny < -0.5. One-line change, idiomatic. Relies on the wall-before-ball creation invariant we currently have (and which is unlikely to change).

Either way I'll remove the print. Which do you want?

B

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Saved. Print gone, floor check is now ev.ny < -0.5, and the comment documents the actual convention (wall is body A, normal points wall→ball, floor normal points up = -y).

Can you also draw the % chance for system 2?

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Saved. Reorganized so the global system-2 metrics (energy, wall boost) are at the top and the per-ball kick metrics (below half, kick chance) sit below.

When there's only a single ball (but only in that case) we need to increase the valves for energy to leave the system. What are possible places we can do this?

Several places, each with different feel implications. Listed roughly from "least invasive to existing systems" to "most":

1. Extend system 2 itself. Currently wall_energy_boost is bounded at [1.0, 1.11] — it never goes below 1. Push the lower bound below 1 (say 0.92) and shift the curve so the boost is symmetric around system_energy ≈ 325: drain at high energy, boost at low energy. Existing machinery, single new constant. Probably the most natural fit since system 2 is already the "regulate around target energy" valve.

2. New single-ball high-speed bypass (mirror of EBB's system 4). EBB's bypass counts consecutive high-speed ball-ball hits and triggers a 30% velocity drop on an S-curve probability — that's the pacing valve for two balls. For one ball, count consecutive high-speed wall hits, same S-curve. Direct conceptual port; adds a "calm beat" rhythm rather than a continuous drain.

3. Wall-hit damping scaled by energy. On every wall hit (any wall), multiply velocity by a small factor like 1 - 0.05 * (system_energy - 300)/300 clamped to [0.95, 1.0]. Continuous, smooth, no probability rolls. Less interesting feel than 1 or 2 — it's just slowly bleeding speed instead of producing pacing variety.

4. Soft speed cap. Currently MAX_BALL_SPEED is a hard clamp (we set it but don't currently apply it for system 2 — but it'd kick in if we did). Replace the clamp with a gradual approach: at >0.85 * MAX start bleeding proportionally. Only drains in extreme regimes; doesn't help when the equilibrium is just "too lively but not maxed out." Probably wrong tool for the job.

5. Periodic timer-driven drop. A timer accumulates while system_energy > threshold; on threshold-cross it fires a 30% velocity scale (à la EBB bypass) and resets. Decoupled from collisions, fires on real-time cadence. Predictable in time but not in motion — could feel arbitrary if it fires mid-bounce.

What I'd actually do

Option 1 is my pick. Reasons:

The one wrinkle for option 1: the symmetric curve target (system_energy ≈ 325) only makes sense for one ball. Two balls would have system_energy roughly doubled, so the same target would look different. We'd need to either gate the drain side on #balls == 1 or scale the curve targets by ball count. The latter generalizes more cleanly but is more thinking.

Option 2 is my second pick — it's the more "EBB-faithful" approach since it explicitly borrows the system 4 pattern. Slightly more code (consecutive-hit counter, S-curve, threshold) but the rhythm feel is more interesting than continuous drain.

Which way do you want to go? Happy to draft either.

Let's try option 2, it seems like a perfect analogue. However this should only be active if there's only a single ball.

Implementation

Three changes — one new state field, one branch in the ball-wall drain, one UI line.

Add to arena_energy state:

high_speed_wall_count = 0,   -- consecutive high-speed wall hits (single-ball bypass only)

Modify arena_energy_update — reset the counter whenever we're not in single-ball mode (so it doesn't carry over and fire spuriously when we drop back to one ball):

function arena_energy_update()
  if #balls ~= 1 then
    arena_energy.high_speed_wall_count = 0
  end

  local total = 0
  -- ... existing code unchanged ...
end

Add system 4 logic in the ball-wall drain — between system 2 and the kick:

      -- Single-ball pacing valve (port of EBB's system 4 high-speed bypass
      -- for the one-ball case). EBB's bypass counts consecutive high-speed
      -- ball-ball hits to inject calm beats; with no other ball to collide
      -- with, we use wall hits instead. Count increments when the ball is
      -- above 0.78*MAX. Each wall hit rolls a cubic_in_out S-curve based on
      -- accumulated count, guaranteed at 9. When it fires, scale velocity by
      -- 0.7 (lose 30%) and reset the counter. Only active when exactly one
      -- ball; multi-ball uses EBB's ball-ball version (added in step 3).
      if #balls == 1 then
        local vx2, vy2 = b.collider:get_velocity()
        if math.length(vx2, vy2) > 0.78 * MAX_BALL_SPEED then
          arena_energy.high_speed_wall_count = arena_energy.high_speed_wall_count + 1
        end
        local n = math.clamp(arena_energy.high_speed_wall_count, 0, 9) / 9
        if random_bool(math.cubic_in_out(n) * 100) then
          arena_energy.high_speed_wall_count = 0
          b.collider:set_velocity(vx2 * 0.7, vy2 * 0.7)
        end
      end

Add UI debug line — gated on single-ball, at y=52:

  if #balls == 1 then
    local n = math.clamp(arena_energy.high_speed_wall_count, 0, 9) / 9
    layer_text(ui_layer, string.format('bypass: %d/9 (%.0f%%)',
      arena_energy.high_speed_wall_count, math.cubic_in_out(n) * 100),
      fonts.main, 4, 52, black())
  end

A note before you run it

The threshold 0.78 * MAX = 349 may be too high for our single-ball equilibrium. If the ball never crosses that speed in normal play, bypass count never increments and the valve never fires. EBB tuned 0.78 for two balls colliding (where one ball can be much faster than the other). If after testing the bypass never opens, drop the multiplier — 0.65 * MAX = 291 or lower.

Saving now.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Saved. Watch the bypass: N/9 counter — should accumulate when the ball is going fast and reset to 0 either when bypass fires or when it visibly drops the ball's speed. If it never accumulates above ~2 in a long session, threshold is too high; if it pegs at 9 and bypass keeps firing every wall hit, threshold is too low or the bypass scale (0.7) is too gentle.

The decrease is too high now, should be gentler.

Pick one (numbers are velocity multiplier, parenthesized is energy lost):

If you don't have a strong preference I'd go with 0.85 — keeps the "calm beat" feel that's the whole point of system 4 while halving EBB's drop. Tell me which.

Let's try 0.92

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Saved. Bypass now drops 8% per fire — the symmetric counterpart to system 2's +11% boost. Watch how the equilibrium settles compared to before; if the ball still ramps up too freely, we can either lower the speed threshold (currently 0.78 * MAX = 349) so bypass fires earlier, or steepen the count curve so the same count triggers more often.

Let's try to make the curve for the bypass weigh more towards the end, so it should be softer on the first ~5-6 hits. Let's make the kick be gentler also vertically, and have no horizontal component to it.

Bypass curve

Changing from cubic_in_out to cubic_in (t³). Same 0-9 range, just back-loaded — chance stays low until the count gets serious:

count cubic_in_out (now) cubic_in (proposed)
1 1.7% 0.1%
2 7.4% 1.1%
3 16.7% 3.7%
4 32.9% 8.8%
5 50.0% 17.1%
6 67.1% 29.6%
7 83.3% 47.1%
8 92.6% 70.2%
9 100% 100%

By hit 5–6 the new curve is at 17/30% vs. the old 50/67% — clearly softer on the first half, then climbing fast at the end. If you want even more back-loading, quart_in would put hit 5 at 9.5% and hit 6 at 20%.

Kick

Changing from (sign(vx) * random_float(0, 4), -16) to (0, -10) — pure vertical, ~62% of current vertical magnitude. Push back: -8 if even that's too strong, -12 if too weak.

Since each kick happens on a floor contact and time_below_half stays elevated until the ball clears the midline, multiple gentle kicks naturally stack until the ball escapes.

Saving.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Saved. Three small edits: bypass curve → cubic_in (back-loaded), bypass UI display matches, kick → pure vertical -10. Watch how the bypass behaves now — should feel like long stretches of "no intervention" punctuated by an occasional hard drop once the count climbs past 6 or 7.

Perfect. Seems good now. Make sure that the negative bypass system is truly only active on 1 ball. Then we can proceed to the next step.

Let me verify the gating by reading the actual code.

Read (E:/a327ex/emoji-ball-bounce/main.lua)

1    --[[
2     Emoji Ball Bounce — Anchor 2.
3   
4     v0 step 1: bare physics scaffold.
5   
6     Open arena ported from Emoji Ball Battles: 480x270 viewport at scale 3,
7     200x200 play area centered, four static rectangle walls wrapped around
8     the interior (each WALL_THICKNESS thick, sized so adjacent walls overlap
9     and seal the corners). One ball at center, EBB physics (restitution 1,
10    no friction, no damping, gravity_scale 1, CCD bullet). No energy systems
11    yet — Box2D will leak energy and the ball will gradually slow. Step 2
12    will add EBB's six-system energy fix; step 3 adds multi-ball spawn keys.
13  
14    Render pipeline (mirrors reference/main.lua, simplified — no effects
15    layer in v0 since there are no projectiles or particles):
16      1. queue draws into game_layer (and bg/ui)
17      2. layer_render(...) flushes queued commands to each layer's FBO
18      3. derive shadow_layer := game_layer + shadow shader
19         derive game_outline := game_layer + outline shader
20      4. composite: bg -> shadow (offset +4,+4) -> outline -> game -> ui
21  ]]
22  
23  require('anchor')({
24    width  = 480,
25    height = 270,
26    title  = 'Emoji Ball Bounce',
27    scale  = 3,
28    filter = 'rough',
29  })
30  
... [382 more lines]

Gating audit

Three places the bypass system touches state, all properly gated:

  1. Counter reset (main.lua:140-142): if #balls ~= 1 then arena_energy.high_speed_wall_count = 0 end. Runs every frame in arena_energy_update. The counter can't grow when multi-ball — it's wiped each frame before any drain runs.
  2. Increment + roll (main.lua:329-339): both wrapped in if #balls == 1. When multi-ball, the count never increments AND the bypass never rolls.
  3. UI display (main.lua:384-389): same gate. Hidden when multi-ball so it doesn't confuse later.

The triple-gating is robust for the current code path. One thing I'd flag for step 3: nothing in update reorders the sequence (spawn → energy_update → drain → destroy_queue), and #balls is queried fresh each access, so as long as ball spawn/kill happens outside the wall drain it stays consistent.

Step 3 proposal

Suggested substeps so we don't dump everything in one go:

3a — Spawn keys + enable ball-ball collisions, no ball-ball drain yet.

3b — Port system 1 (ball energy boost on ball-ball, +9% per collision).

3c — Port systems 3 (redistribution) + 4 (high-speed bypass) + 5 (low-horizontal kick).

3d — Cleanup. Remove debug HUD lines we don't need anymore. Decide whether the single-ball wall-bypass coexists with EBB's ball-ball bypass when multi-ball, or only the latter is active. Probably the latter — system 4 covers pacing once there's at least one ball-ball pair.

Want to start with 3a? Or rearrange the substeps?

Yes, it's fine as is, go ahead.

Ah, I remember now. One of the issues that one of the systems solves for ball-ball collisions is actually spreading the collision more equally among balls. If this isn't done, you generally get one fast moving ball, it hits the other ball, the other ball becomes fast, and the original becomes slow. So the momentum accumulates in one ball and is removed from the other, which looks too predictable and not interesting enough. So yes, add whatever new systems you were going to add for step b) now.

Step 3b/c combined — porting systems 1, 3, 4, 5

Five edits:

  1. Add BALL_ENERGY_BOOST = 1.09 to constants block.
  2. Extend arena_energy state with high_speed_hit_count and low_horizontal_hit_count.
  3. Extend arena_energy_update to reset these counters when #balls < 2.
  4. Add a full ball-ball collision drain with systems 1, 3, 4, 5 in EBB-faithful order: bypass → redistribution → boost → speed cap → low-horizontal kick.
  5. Restructure UI so single-ball debug (below half / kick / wall-bypass) and multi-ball debug (ball-ball bypass / low-horiz) are separate modes.

The main piece is the new ball-ball drain. Mirrors EBB's order from emoji-ball-battles/main.lua:652-790 — most important constants verbatim:

for _, ev in ipairs(collision_entities_begin('ball', 'ball')) do
  local a, b = ev.a, ev.b
  if a and b and not a._dead and not b._dead then
    local vx_a, vy_a = a.collider:get_velocity()
    local vx_b, vy_b = b.collider:get_velocity()
    local speed_a = math.length(vx_a, vy_a)
    local speed_b = math.length(vx_b, vy_b)
    local max_speed = math.max(speed_a, speed_b)

    -- System 4: high-speed bypass (ball-ball). cubic_in_out S-curve over
    -- 0..9 consecutive high-speed hits, EBB's full 0.7 scale (lose 30%).
    if max_speed > 0.78 * MAX_BALL_SPEED then
      arena_energy.high_speed_hit_count = arena_energy.high_speed_hit_count + 1
    end
    local n = math.clamp(arena_energy.high_speed_hit_count, 0, 9) / 9
    local bypass = random_bool(math.cubic_in_out(n) * 100)
    if bypass then
      arena_energy.high_speed_hit_count = 0
      vx_a, vy_a = vx_a * 0.7, vy_a * 0.7
      vx_b, vy_b = vx_b * 0.7, vy_b * 0.7
    else
      -- System 3: energy redistribution. Probability scales with max_speed.
      -- Picks a target ratio from N(0.5, stddev), blends current ratio
      -- toward it. stddev shrinks 0.3 -> 0.1 with speed. Solves the "fast
      -- ball ping-ponging slow ball" failure mode.
      local speed_ratio = math.remap(max_speed, 0, MAX_BALL_SPEED, 0, 1)
      if random_bool(speed_ratio * 100) then
        local energy_a = vx_a*vx_a + vy_a*vy_a
        local energy_b = vx_b*vx_b + vy_b*vy_b
        local total_energy = energy_a + energy_b
        if total_energy > 0 and energy_a > 0.01 and energy_b > 0.01 then
          local ratio_a = energy_a / total_energy
          local stddev = math.remap(speed_ratio, 0, 1, 0.3, 0.1)
          local target = random_normal(0.5, stddev)
          local new_ratio_a = math.clamp(math.lerp(speed_ratio, ratio_a, target), 0.05, 0.95)
          local scale_a = math.sqrt((total_energy * new_ratio_a)       / energy_a)
          local scale_b = math.sqrt((total_energy * (1 - new_ratio_a)) / energy_b)
          vx_a, vy_a = vx_a * scale_a, vy_a * scale_a
          vx_b, vy_b = vx_b * scale_b, vy_b * scale_b
        end
      end
    end

    -- System 1: ball energy boost. Compensates Box2D leakage. Skip on bypass.
    if not bypass then
      vx_a, vy_a = vx_a * BALL_ENERGY_BOOST, vy_a * BALL_ENERGY_BOOST
      vx_b, vy_b = vx_b * BALL_ENERGY_BOOST, vy_b * BALL_ENERGY_BOOST
    end

    -- Speed cap (preserves direction).
    local s_a = math.length(vx_a, vy_a)
    if s_a > MAX_BALL_SPEED then local k = MAX_BALL_SPEED/s_a; vx_a, vy_a = vx_a*k, vy_a*k end
    local s_b = math.length(vx_b, vy_b)
    if s_b > MAX_BALL_SPEED then local k = MAX_BALL_SPEED/s_b; vx_b, vy_b = vx_b*k, vy_b*k end

    -- System 5: low-horizontal kick. Linear chance, guaranteed at 4 hits.
    if math.abs(vx_a) + math.abs(vx_b) < 0.25 * MAX_BALL_SPEED then
      arena_energy.low_horizontal_hit_count = arena_energy.low_horizontal_hit_count + 1
      local kick_chance = math.clamp(arena_energy.low_horizontal_hit_count, 0, 4) / 4
      if random_bool(kick_chance * 100) then
        arena_energy.low_horizontal_hit_count = 0
        vx_a = random_sign() * random_float(100, 200)
        vx_b = random_sign() * random_float(100, 200)
      end
    else
      arena_energy.low_horizontal_hit_count = 0
    end

    a.collider:set_velocity(vx_a, vy_a)
    b.collider:set_velocity(vx_b, vy_b)

    -- Spring pull both balls, intensity scaled by combined speed.
    local intensity = math.remap(speed_a + speed_b, 0, 800, 0, 1)
    spring_pull(a.spring, 'hit', intensity * 0.4)
    spring_pull(b.spring, 'hit', intensity * 0.4)
  end
end

Saving all five edits.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

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Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Saved. Test plan:

Tell me what you see — especially the redistribution feel (does the "fast ball ping-ponging slow ball" pattern still appear?) and whether the global counters get pegged at 9 with many balls.

Yep, the balls are all fine and it works great. What's next?

Where we are

Physics layer is done. Six EBB-faithful energy systems active, single-ball stable, multi-ball stable, redistribution working, gentle horizontal-bias kick handling the flat-bouncing case. That's the whole "make balls bounce forever in interesting ways" foundation the design depends on.

What's next — a few directions

Sorted from most-aligned-with-design.md to least:

1. Event bus + chips/mult + first cards (the design's stated next step). Build the architectural backbone for the entire scoring layer:

2. Round structure first. A fixed-duration round timer with round_start / round_end events, score = chips × mult resolved at round end, threshold check, win/lose flow. Doesn't need cards — chips and mult start at 0 and stay 0 — but establishes the loop. Then layer cards on top in a follow-up. Slightly out of design.md order but makes the eventual playtest closer to "real" since score has consequence.

3. Polish the physics layer first. What we have works but is rougher than EBB visually: no SFX (the ball_wall.ogg and concrete_*.ogg are sitting unused in assets/), no squash/stretch on wall hits, no hit VFX on ball-ball collisions, no spring pulls beyond a single uniform amount. Half a session of work to bring it to EBB-level polish. Pure visual/audio improvement, no functional change. Could be done now or deferred until everything else works and we're "feature complete."

4. Clean up the debug HUD. The current readouts (energy, wall boost, below half, kick chance, bypass, low-horiz) were tuning aids. Now that the physics is locked in, they're clutter. Either strip them entirely, gate behind an F1 toggle, or replace with the score HUD. ~5 minutes of work, but probably should happen alongside (1) anyway.

What I'd actually do

(1) — event bus + chips/mult + first cards. Reasons:

The cost of (1): ~1-2 sessions of architectural work before you can press buttons and see numbers go up. (2)/(3)/(4) all give a faster "I made a thing" satisfaction.

Concrete sub-steps if we go with (1):

Want to go with (1)? Or rearrange?

Let's do 3, port over most/all effects when it comes to ball-ball and ball-wall collisions except for sounds, which we'll do in batch later.

Let me find EBB's ball squash logic — that's the main visual polish missing.

Grep (function ball:squash|squash_x|squash_y|squash()

920:    ball_object:squash(event.normal_x, event.normal_y, 0.75*intensity)
1983:  self.spring:add('squash_x', 1)
1984:  self.spring:add('squash_y', 1)
2225:      self.spring:pull('squash_y', 0.5, 3, 0.5)
2226:      self.spring:pull('squash_x', -0.25, 3, 0.5)
2236:  local squash_x = self.spring.squash_x.x
2237:  local squash_y = self.spring.squash_y.x
2264:          {self.x, self.y, self.thrust_angle, squash_x*thrust_stretch_ai, squash_y*thrust_squeeze_ai},
2274:    game:push(self.x + bsx, self.y + bsy, self.thrust_angle, squash_x*thrust_stretch, squash_y*thrust_squeeze)
2280:    game:push(self.x + bsx, self.y + bsy, 0, squash_x, squash_y)           -- world-aligned squash (no rotation)
2910:function ball:squash(normal_x, normal_y, amount)
2914:    self.spring:pull('squash_x', amount, 3, 0.5)
2915:    self.spring:pull('squash_y', -amount*0.5, 3, 0.5)
2918:    self.spring:pull('squash_y', amount, 3, 0.5)
2919:    self.spring:pull('squash_x', -amount*0.5, 3, 0.5)

Read (E:/a327ex/emoji-ball-battles/main.lua)

2905   self.ball_flashing = true
2906      self.timer:after(duration, 'ball_flash', function() self.ball_flashing = false end)
2907    end
2908    
2909    -- Squash ball on wall collision: horizontal wall squashes y, vertical wall squashes x
2910    function ball:squash(normal_x, normal_y, amount)
2911      amount = amount or 0.3
2912      if math.abs(normal_y) > math.abs(normal_x) then
2913        -- Horizontal wall (floor/ceiling): squash y, stretch x
2914        self.spring:pull('squash_x', amount, 3, 0.5)
2915        self.spring:pull('squash_y', -amount*0.5, 3, 0.5)
2916      else
2917        -- Vertical wall (left/right): squash x, stretch y
2918        self.spring:pull('squash_y', amount, 3, 0.5)
2919        self.spring:pull('squash_x', -amount*0.5, 3, 0.5)
2920      end
2921    end
2922    
2923    -- Start ball movement (called when game unpauses)
2924    function ball:start_moving()
2925      self.collider:set_gravity_scale(1)
2926      self.collider:apply_impulse(an.random:sign()*an.random:float(5, 10), an.random:float(-10, 10))
2927      self.collider:set_angular_velocity(self.base_angular_velocity)
2928    end
2929

Read (E:/a327ex/emoji-ball-battles/main.lua)

2235   -- Draw ball
2236      local squash_x = self.spring.squash_x.x
2237      local squash_y = self.spring.squash_y.x
2238      local hit_scale = self.spring.hit.x
2239    
2240      -- Ball shake offset
2241      local shake_fx = self.ball_shake:get_transform()
2242      local bsx, bsy = shake_fx.x, shake_fx.y
2243    
2244      -- Thrust squash values (used by both ball and weapon draw)
2245      local squash_t, stretch_amount, squeeze_amount = 0, 0, 0
2246      if self.thrusting then
2247        squash_t = math.sin(self.thrust_progress*math.pi)
2248        local thrust_speed = math.lerp(math.quad_out(self.thrust_progress), self.thrust_start_speed, self.thrust_end_speed)
2249        local speed_factor = math.clamp(math.remap(thrust_speed, 400, 600, 0, 1), 0, 1)
2250        stretch_amount = math.lerp(speed_factor, 0.4, 0.6)
2251        squeeze_amount = math.lerp(speed_factor, 0.2, 0.3)
2252      end
2253    
2254      -- Spawn afterimages during thrust
2255      if self.thrusting then
2256        self.afterimage_timer = self.afterimage_timer + dt
2257        if self.afterimage_timer >= 0.03 then
2258          self.afterimage_timer = 0
2259          local thrust_stretch_ai = 1 + stretch_amount*squash_t
2260          local thrust_squeeze_ai = 1 - squeeze_amount*squash_t
2261          self.parent.effects:add(afterimage(self.x, self.y, {
2262            layer = game, image = self.image, duration = 0.15,
2263            pushes = {
2264              {self.x, self.y, self.thrust_angle, squash_x*thrust_stretch_ai, squash_y*thrust_squeeze_ai},
... [45 more lines]

Bash (grep -n "^function spring_pull|^function spring_add" E:/a327ex/emoji-ball-bounc...)

40:function spring_add(s, name, x, frequency, bounce)
63:function spring_pull(s, name, force, frequency, bounce)

Grep (function math.circ_in\b|function math.cubic_in_out\b)

508:function math.cubic_in_out(t)
606:function math.circ_in(t)

Let me also check what EBB's hit_effect does, and whether ball-ball gets any of it.

Grep (^function arena:hit_effect|self:hit_effect)

876:    self:hit_effect(event.point_x, event.point_y, hit_multiplier)
1031:    self:hit_effect(event.point_x, event.point_y)
1236:    self:hit_effect(projectile_object.x, projectile_object.y)
1331:    self:hit_effect(projectile_object.x, projectile_object.y)
1373:      self:hit_effect(cd_object.x, cd_object.y)
1433:    self:hit_effect(projectile_object.x, projectile_object.y)
1481:    self:hit_effect(effect_x, effect_y, attacker.hit_particle_multiplier)
1584:function arena:hit_effect(x, y, multiplier)

Read (E:/a327ex/emoji-ball-battles/main.lua)

1584 function arena:hit_effect(x, y, multiplier)
1585      multiplier = multiplier or 1.0
1586      local probability = self:get_hit_stop_probability()
1587      local hit_effect_chance = 35 + 65*probability  -- 35% at rapid hits, 100% at fresh hit
1588    
1589      if an.random:bool(hit_effect_chance) then
1590        self.effects:add(hit_effect(x, y, {scale = 1.35*multiplier}))
1591      else
1592        self.effects:add(hit_circle(x, y, {radius = 9*multiplier}))
1593        local particle_count = math.floor(an.random:int(2, 4)*multiplier)
1594        for i = 1, particle_count do
1595          self.effects:add(hit_particle(x, y, {velocity = multiplier*an.random:float(100, 250), duration = multiplier*an.random:float(0.3, 0.5)}))
1596        end
1597      end
1598    end
1599    
1600    function arena:hit_stop(duration)
1601      duration = duration or 0.1
1602      local probability = self:get_hit_stop_probability()
1603      if an.random:bool(100*probability) then
1604        an:hit_stop(duration)
1605      end
1606      self.time_since_last_hit = 0
1607    end
1608

What EBB actually does on these collisions

After reading the relevant chunks of EBB, the effects landscape is narrower than I expected:

event EBB effects
ball-wall directional squash (intensity-shaped by speed) + sound. No particles, no hit_circle.
ball-ball spring pull on both balls (intensity-scaled) + sound. No squash, no particles, no hit_circle.
weapon-weapon hit_effect (= hit_circle + 2-4 hit_particles) + hit_stop + camera shake + flash + spring pull

So EBB-faithful porting means just one new thing: directional squash on wall hits. Ball-ball already has the intensity-scaled spring pull (we ported that with system 1).

Three interpretations of "most/all effects"

A — EBB-faithful only. Add ball:squash and wire it into wall hits. Tiny change. Ball-ball stays as it is. This matches what EBB looks like.

B — EBB-faithful + visual upgrade for ball-ball. Add squash on wall hits AND borrow the weapon-weapon style (hit_circle + a couple of hit_particles) for ball-ball collisions. Requires bringing back the effects layer + hit_circle / hit_particle classes from reference/main.lua. Ball-ball collisions become noticeably meatier than EBB's. Wall hits stay clean (they're too frequent to pile particles on).

C — Full effects pass. Same as B but with particles/hit_circle on wall hits too. Probably too noisy — wall hits happen multiple times per second per ball.

I'd lean B. Wall hits are a constant background pulse, so the directional squash is the right amount of feedback there. Ball-ball is a discrete event that deserves a bigger flourish — and once we have the effects layer back, we'll need it anyway when projectiles return as a card mechanic. Doing it now keeps the architecture aligned.

Which one?

Let's do A.

Three small edits.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Saved. Should see directional flatten on every wall hit now — strongest at high speeds, barely visible at low speeds. Floor/ceiling hits flatten vertically, side wall hits compress horizontally.

When you've confirmed it looks right, want to circle back and pick the next direction (event bus + cards, round structure, or further polish)?

The squash needs to be more subtle than now.;

Cutting the magnitude roughly in half. Change the multiplier in on_wall_hit from 0.75 to 0.4:

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Saved. Tell me if 0.4 still feels off and we'll dial down further.

We're doing both squash and normal spring pull, right? Did the original do both? And are the values the same there from here?

Grep (spring:pull('hit')

788:    ball_a.spring:pull('hit', intensity*0.4, 3, 0.7)
789:    ball_b.spring:pull('hit', intensity*0.4, 3, 0.7)
1325:    projectile_object.spring:pull('hit', 0.5, 3, 0.5)
1369:      cd_object.spring:pull('hit', 0.5, 3, 0.5)
2410:  self.spring:pull('hit', 0.3, 3, 0.7)
2515:  self.spring:pull('hit', 0.25, 3, 0.5)
2681:  self.spring:pull('hit', 0.25, 3, 0.5)
4068:  self.spring:pull('hit', 0.3, 3, 0.5)  -- pop on spawn
4246:  self.spring:pull('hit', 0.5*intensity, 3, 0.5)

Read (E:/a327ex/emoji-ball-bounce/anchor/spring.lua)

1    --[[
2     spring — procedural damped spring animation.
3   
4     Usage:
5       self.spring = spring_new()                       -- in constructor
6       spring_add(self.spring, 'scale', 1, 5, 0.5)      -- name, initial value, frequency, bounce
7       spring_pull(self.spring, 'scale', 0.3)           -- apply impulse
8       spring_update(self.spring, dt)                   -- in update
9   
10      -- Read current value:
11      local s = self.spring.scale.x
12  
13    A default 'main' spring at value 1 is created on spring_new() for convenience.
14    You typically use spring.main.x as a single pulsing value for hit flashes,
15    click feedback, etc.
16  
17    Spring parameters:
18      frequency - oscillations per second (higher = faster)
19      bounce    - bounciness 0-1 (0=no overshoot, 1=infinite oscillation)
20      bounce=0.5 is moderate overshoot, common for hit reactions.
21  ]]
22  
23  --[[
24    spring_new()
25    Creates a new spring container with a default 'main' spring at value 1.
26  ]]
27  function spring_new()
28    local s = {
29      _names = {},
30    }
... [70 more lines]

Audit results

No, EBB only does squash on wall hits — not the spring 'hit' pull. I have us doing both, which adds a uniform pop on top of the directional squash that EBB doesn't have. And the values are off in two more places too:

EBB us (current)
spring 'hit' pull on wall hit (none) force 0.3, default freq/bounce
spring 'hit' pull on ball-ball force intensity*0.4, freq 3, bounce 0.7 force intensity*0.4, default freq/bounce
squash pull (squash_x / squash_y) EBB amount 0.75*intensity, freq 3, bounce 0.5 our amount 0.4*intensity, freq 3, bounce 0.5 ✓
spring_add for 'hit' freq/bounce not set (engine defaults) same

The default frequency in our framework is 5 (faster oscillation) and bounce is 0.5 (less overshoot). EBB ball-ball pulls explicitly pass 3, 0.7 — slower + bouncier, so the pulse reads longer with a visible overshoot. Our pulls don't, so on ball-ball we get a faster, more damped response than EBB.

The squash itself uses the right params (we pass 3, 0.5 explicitly), so the squash motion matches EBB. Just the magnitude differs (0.4 vs 0.75) — and that was your call.

Proposed fix to align with EBB

  1. Bake frequency/bounce into the springs at add time so they're correct without needing to pass on every pull:
    • spring_add(self.spring, 'hit', 1, 3, 0.7)
    • spring_add(self.spring, 'squash_x', 1, 3, 0.5)
    • spring_add(self.spring, 'squash_y', 1, 3, 0.5)
  2. Remove the spring 'hit' pull from on_wall_hit — only squash fires on wall hits, EBB-faithful.

After this: ball-wall is just the directional squash. Ball-ball is the spring 'hit' pulse with EBB's slower/bouncier feel. Cleaner separation of "wall = directional flatten" from "ball-ball = uniform pop."

Want me to do both?

Yes.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Saved. Wall hits are now pure directional squash; ball-ball is uniform pop with the slower/bouncier EBB feel.

Perfect now. Let's end this session. Update any files that need to be update in terms of todos and so on. Then end it. Call it "EBB Ball Bounce Mechanics"

I'll update the file headers to reflect the actual state, then call the end-session skill.

Edit (E:/a327ex/emoji-ball-bounce/main.lua)

The file E:/a327ex/emoji-ball-bounce/main.lua has been updated successfully. (file state is current in your context — no need to Read it back)

Edit (E:/a327ex/emoji-ball-bounce/design.md)

The file E:/a327ex/emoji-ball-bounce/design.md has been updated successfully. (file state is current in your context — no need to Read it back)

Files updated. Calling end-session.

Skill 

Launching skill: end-session

Base directory for this skill: E:\a327ex.claude\skills\end-session

End Session Workflow

This skill is invoked from the same conversation where the work was done. You already have the full session context in memory — you do NOT need to read the transcript.

Step 1: Get Session Info

Ask the user for the session title (max 30 characters). Examples: "Anchor Phase 10 Part 5", "Physics Arena Setup", "Timer System Fix", "Thalien Lune Design".

Determine the project yourself from your session context — you know which repo(s) were worked on, which files were created/modified, and where they live. No need to ask. See Step 6 for the list of known project roots; if the session touched something outside the list, infer the root from the paths you actually edited.

Step 2: Write Summary

Write the summary from your conversation memory. You have the full session context — no need to read any files.

The summary should be thorough and detailed. Each major topic deserves its own section with multiple specific bullet points. Don't compress — expand.

Purpose: These summaries serve as searchable records. Future Claude instances will grep through past logs to find how specific topics were handled. The more detail you include, the more useful the summary becomes for finding relevant context later.

Format (this is just an example structure — adapt sections to match what actually happened):

# [Title]

## Summary

[1-2 sentence overview of the session's main focus]

**[Topic 1 - e.g., "Spring Module Implementation"]:**
- First specific detail about what was done
- Second detail - include file names, function names
- User correction or feedback (quote if notable)
- Technical decisions and why

**[Topic 2 - e.g., "Camera Research"]:**
- What was researched
- Key findings
- How it influenced implementation

**[Topic 3 - e.g., "Errors and Fixes"]:**
- Specific error message encountered
- Root cause identified
- How it was fixed

[Continue for each major topic...]

---

[Rest of transcript follows]

Rules: - Be thorough — If in doubt, include more detail, not less. Each topic should be as detailed as possible while still being a summary. - Think searchability — Future instances will search these logs. Include keywords, function names, error messages that someone might grep for. - One section per major topic — Don't combine unrelated work into one section - Chronological order — Sections should match conversation flow - Specific details — Error messages, file names, function names, parameter values - Include user quotes — When user gave notable feedback, quote it (e.g., "k/d variables are not intuitive at all") - Weight planning equally — Research, proposals, alternatives considered, user feedback on approach are as important as implementation - Weight problems solved — Errors, root causes, fixes, user corrections all matter - Technical specifics — Include formulas, API signatures, parameter changes when relevant

Step 3: Get User Approval

Show the title and summary to the user. Wait for approval before proceeding. If they have corrections, fix them.

Step 4: Convert Transcript and Write Log File

# Find recent sessions (Claude + Cursor; see script). Same script lives in Anchor2:
python E:/a327ex/Anchor2/scripts/find-recent-session.py --limit 5
# or: python E:/a327ex/Anchor/scripts/find-recent-session.py --limit 5

The script shows sessions sorted by when they ended. The first result is the current conversation (since end-session was invoked here). Use it.

Convert the transcript to markdown and write the log file with the approved summary as header:

python E:/a327ex/Anchor2/scripts/jsonl-to-markdown.py [SESSION_PATH] E:/a327ex/anchor.blot.im/logs/[slug].md
# or: python E:/a327ex/Anchor/scripts/jsonl-to-markdown.py ...

The same script auto-detects Claude Code JSONL vs Cursor/Composer agent JSONL (~/.cursor/projects/.../agent-transcripts/...). For Composer sessions, use find-recent-session.py (it merges both sources) and pick the [cursor] line for the current chat.

Use lowercase hyphenated slug derived from the title (e.g., "anchor-primitives-hitstop-animation").

Then replace the default header (# Session YYYY-MM-DD...) with the approved title and summary.

Step 5: Sync Context Files to Blot

cp E:/a327ex/.claude/CLAUDE.md E:/a327ex/anchor.blot.im/context/CLAUDE.md
cp E:/a327ex/Anchor/docs/* E:/a327ex/anchor.blot.im/context/

When the session was Anchor2 (optional):

cp E:/a327ex/Anchor2/.claude/CLAUDE.md E:/a327ex/anchor.blot.im/context/CLAUDE_ANCHOR2.md

Step 6: Commit Project Repo

Identify the project repo(s) worked on this session from your own context — you already know which repos were touched and which files changed. For the common projects, here are the canonical staging commands:

Project Root Stage command
Anchor E:/a327ex/Anchor git add docs/ framework/ engine/ scripts/ reference/
Anchor2 E:/a327ex/Anchor2 git add framework/ engine/ arena/ reference/ scripts/ docs/ .claude/
emoji-ball-battles E:/a327ex/emoji-ball-battles git add -A
orblike E:/a327ex/orblike git add -A
thalien-lune E:/a327ex/thalien-lune git add -A

For a project not listed, infer the root from the files you actually created or modified this session and stage those. If multiple candidate roots look valid, ask the user which files to stage.

cd into the project root, stage, run git status to verify before committing.

IMPORTANT — FULL SUMMARY IN COMMIT: The commit message MUST include the FULL summary from the log file. Read the summary back from the log file to ensure nothing is missing.

IMPORTANT — COMMIT METHOD: The summary contains backticks, special characters, and markdown that WILL break heredocs and git commit -m. ALWAYS use the file-based method below. NEVER try a heredoc first — it will fail and produce a malformed commit that needs amending.

Commit using a temporary file (extracts only the summary text, not the markdown heading or ## Summary line):

# Extract summary: skip line 1 (# Title) and line 3 (## Summary), take lines 4 onward until the --- separator
awk 'NR>=4 && /^---$/{exit} NR>=4{print}' E:/a327ex/anchor.blot.im/logs/[slug].md > /tmp/commit_msg.txt

# Prepend the title (plain text, no #) and append attribution
sed -i "1i [Title]\n" /tmp/commit_msg.txt
printf "\nGenerated with [Claude Code](https://claude.com/claude-code)\n\nCo-Authored-By: Claude <noreply@anthropic.com>\n" >> /tmp/commit_msg.txt

git commit -F /tmp/commit_msg.txt

Step 7: Push Both Repos

# Push project repo to GitHub
git push origin main

# Push Blot repo (logs and context are already there)
cd E:/a327ex/anchor.blot.im && git add -A && git commit -m "[Title]" && git push origin master

Step 8: Confirm

Tell the user: - Commit hash - That GitHub push succeeded - That Blot push succeeded

ARGUMENTS: EBB Ball Bounce Mechanics

Title: "EBB Ball Bounce Mechanics" (25 chars ✓)

Summary

# EBB Ball Bounce Mechanics

## Summary

Built out the physics scaffold for emoji-ball-bounce: a fresh main.lua at the project root porting EBB's collision energy systems faithfully, with single-ball-only adaptations and EBB-faithful directional squash on wall hits. Six energy systems plus two single-ball additions are now active and stable across all ball counts.

**Initial assessment and planning:**
- Project state: only one git commit ("Emoji Ball Bounce Exploration"), clean working tree. The "scaffold" described in design.md (single ball in rotating chamber, Ricochet-style special-bounce) lived in reference/main.lua, not at the project root. run.bat would have failed to launch because no main.lua existed.
- The reference scaffold was Ricochet-style (chamber + special-bounce variety), at odds with design.md's "open arena, EBB-style energy systems" intent.
- AskUserQuestion used to lock in 3 decisions: Path = Physics rebuild first, Source = Read EBB main.lua end-to-end, Entry point = New main.lua at root with reference/main.lua left intact.
- Followups locked: ball count = runtime spawn keys, projectiles = remove for v0, arena = match EBB exactly (480x270 at scale 3, 200x200 arena), debug HUD = none initially. Late calls: ball rotation free per EBB (no fixed_rotation), 480x270 resolution.

**EBB energy system extraction (emoji-ball-battles/main.lua):**
- Read EBB's six-system energy logic verbatim. Constants: MAX_BALL_SPEED = 448, WORLD_GRAVITY_Y = 384, BALL_ENERGY_BOOST = 1.09, MIN/MAX_WALL_ENERGY_BOOST = 1.0/1.11.
- Six systems documented: (1) ball energy boost on ball-ball, (2) wall energy boost probabilistic shaped by system_energy, (3) energy redistribution to solve "fast ball ping-pongs slow ball", (4) high-speed bypass with cubic_in_out S-curve and 0.7 scale, (5) low-horizontal kick with linear chance, (6) stuck-ball hop per-ball update logic.
- Critical bug found in EBB's single-ball case: system_energy is only updated on ball-ball collisions (EBB main.lua line 664), so for one ball it would stay frozen at the initial 250 forever. Fix: refresh system_energy each frame from current ball speeds.

**Step 1: bare scaffold (main.lua at root):**
- 480x270 viewport at scale 3, 200x200 EBB arena centered, four sealed-corner static walls (each WALL_THICKNESS=200 thick, wrapped so corners overlap and are filled).
- Wall color: color_mix(fg, yellow, 0.1). Sky gradient bg, handcam shake camera, per-layer outline + drop shadow shaders.
- Ball: EBB physics (restitution 1, no friction, no damping, gravity 1, CCD bullet, free rotation per EBB).
- Render pipeline: bg → game queue → derive shadow + outline → composite (bg → shadow @ +4,+4 → outline → game → ui). Effects layer omitted since v0 has no projectiles/particles.
- No energy systems yet — Box2D leakage caused the ball to slow gradually as expected.

**Step 2: single-ball energy systems + horizontal-bias kick:**
- Initially proposed all 6 systems gated by ball count, but user pushed back: "Let's only add the system that fires when we have a single ball. Then when we add more balls we'll add the other systems."
- Pared down to systems 2 (wall energy boost) and 6 (stuck-ball hop) only — the only EBB systems active for single ball.
- arena_energy state table: system_energy, wall_energy_boost, wall_boost_chance.
- arena_energy_update() recomputes system_energy each frame from sum of live ball speeds, then derives wall_boost_chance (quad_out 100%→0% over energy 100→600) and wall_energy_boost (sine_out interpolating 1.11→1.0 over energy 250→400).
- ball:update gained system 6: when y + radius > ARENA_FLOOR_Y - 20 and |vy| < 15 for 0.5–1.5s, apply impulse (sign(vx) * random_float(0, 6), -24).
- Added LanaPixel.ttf font asset (copied from EBB), debug HUD line "energy: %.0f" on ui_layer.

**Time-below-half tracking and horizontal-bias kick:**
- User identified the flat-bouncing failure mode: vy oscillates through zero on every bounce so an instantaneous h/v ratio is junk. Better metric: time the ball has spent below the arena midline without crossing it.
- Per-ball self.time_below_half: resets to 0 when self.y < ARENA_CY, accumulates dt otherwise.
- Curve picked: quad_in over 1–8s window (0% at 1s, 100% at 8s, gentle escalation). Chance computed per floor contact: math.quad_in(clamp((time_below_half - 1) / 7, 0, 1)) * 100.
- Kick: pure vertical, magnitude -10. Initial proposal had horizontal component (sign(vx) * random_float(0, 4), -16) but user gentled it: "gentler also vertically, and have no horizontal component."
- Kick doesn't reset time_below_half — only the ball actually crossing the midline does, so insufficient kicks roll again on subsequent floor contacts.

**Collision normal convention investigation:**
- Initial floor detection used position-based check (b.y + b.radius >= ARENA_FLOOR_Y - 0.5) because I had assumed ev.ny was unreliable due to body_a/body_b swap in framework's collision_entities_begin. User asked me to print ev.ny to verify.
- Found: ev.ny is consistently -1 for floor hits in this engine. The framework's collision_entities_begin swaps body_a/body_b based on tag order (so ev.a is always the ball) but does NOT flip the normal vector. The Anchor 2 engine's normal is "from body A to body B" per anchor.c:529, and Box2D records the wall as body A (created before ball). So normal points wall→ball, which for floor is upward (-y).
- I had been wrong about the framework being unreliable. Switched to ev.ny < -0.5 for floor detection. Documented the convention in comments for when ball-ball collisions land in step 3.
- EBB's event.normal_y > 0.5 works in EBB because EBB's ordering is opposite — different engine, different convention.

**Single-ball bypass system (port of EBB's system 4):**
- User identified that single-ball needs an energy-out valve (analogous to system 4 for multi-ball). Chose option 2 from design discussion: mirror EBB's high-speed bypass for the one-ball case using wall hits instead of ball-ball collisions.
- arena_energy.high_speed_wall_count: counts consecutive wall hits where ball speed > 0.78 * MAX_BALL_SPEED. Reset to 0 in arena_energy_update when #balls ~= 1 so it doesn't carry over.
- Initially used cubic_in_out S-curve (EBB's curve) and 0.7 scale. User said decrease was too high → 0.92. User then asked for back-loaded curve "softer on the first ~5-6 hits" → switched to cubic_in (t³). New table: hit 5 = 17%, hit 6 = 30%, hit 9 = 100% (vs cubic_in_out's 50%/67%/100%).
- Triple-gated: counter reset (arena_energy_update), increment + roll (wall drain), UI display — all guarded by #balls == 1.

**Step 3a: multi-ball spawn keys:**
- Bound space → spawn_ball_random (random arena position with margin from walls), backspace → reset_balls (entity_kill all + clear array + spawn one fresh at center).
- Enabled physics_enable_collision('ball', 'ball') so balls bounce off each other physically.
- Input handling placed at end of update() after process_destroy_queue, mirroring reference/main.lua's pattern (avoid invalidating in-flight Box2D body handles mid-frame).

**Step 3b/c: ball-ball energy systems (1, 3, 4, 5):**
- User flagged the redistribution problem from memory: "if not done, you generally get one fast moving ball, it hits the other ball, the other ball becomes fast, and the original becomes slow. So the momentum accumulates in one ball." This is exactly EBB's system 3.
- Added BALL_ENERGY_BOOST = 1.09 constant, plus high_speed_hit_count and low_horizontal_hit_count to arena_energy (reset when #balls < 2).
- Full ball-ball drain ported EBB-faithfully: order is bypass first, then redistribution OR boost (mutually exclusive with bypass), speed cap, low-horizontal kick. Plus intensity-scaled spring 'hit' pull on both balls.
- System 3 redistribution uses random_normal(0.5, stddev) where stddev shrinks 0.3 → 0.1 with speed_ratio. new_ratio_a clamped to [0.05, 0.95]. scale_a = sqrt((total_energy * new_ratio_a) / energy_a).
- System 4 ball-ball uses EBB's full 0.7 scale and cubic_in_out curve (different from single-ball's 0.92 / cubic_in).
- System 5 fires with random_sign() * random_float(100, 200) horizontal impulse on both balls when |vx_a| + |vx_b| < 0.25 * MAX.
- UI restructured: single-ball mode shows below half / kick chance / wall-bypass; multi-ball mode shows ball-ball bypass / low-horiz.

**Step 4: visual polish (option A — EBB-faithful only):**
- User picked option A from three offered: minimum EBB-faithful (just squash on wall hits, ball-ball stays as-is). Rejected option B (squash + hit_circle/particles on ball-ball) and option C (full effects pass).
- Added 'squash_x' and 'squash_y' springs to ball, rest=1, freq=3, bounce=0.5.
- ball:squash(normal_x, normal_y, amount) method ported from EBB: horizontal wall (|ny| > |nx|) stretches x by +amount, compresses y by -amount*0.5; vertical wall does the opposite. Asymmetric 0.5 ratio gives a teardrop flatten rather than rectangular.
- ball:on_wall_hit computes intensity from velocity using EBB's two-segment easing: cubic_in_out below intensity 0.5, circ_in above. Applied as 0.4 * intensity (gentled from EBB's 0.75 per user feedback).
- ball:draw restructured with two-level transform: outer push for world-aligned squash (squash_x, squash_y), inner push for rotation + uniform hit_scale.

**EBB audit and spring parameter alignment:**
- User asked "are the values the same there from here?" — audited and found three discrepancies:
  1. We pulled spring 'hit' at force 0.3 on every wall hit; EBB does NOT (only squash fires on wall hits).
  2. Our ball-ball spring pull used default freq=5 / bounce=0.5; EBB uses explicit 3, 0.7 (slower oscillation, more overshoot).
  3. Squash params already matched (both at 3, 0.5).
- Fix: bake EBB's freq/bounce into spring_add calls (hit at 3, 0.7; squash_x and squash_y at 3, 0.5), and remove the extraneous spring_pull('hit', 0.3) from on_wall_hit. Final result: wall hits are pure directional squash; ball-ball collisions get the slower/bouncier EBB feel.

**Tuning iterations and user pushback:**
- Squash magnitude: 0.75 (EBB) → 0.4 per "squash needs to be more subtle." Peak now ~1.4× stretch / ~0.8× compress (was ~1.75× / ~0.6×).
- Bypass scale (single-ball): 0.7 → 0.92 per "decrease is too high now, should be gentler."
- Bypass curve (single-ball): cubic_in_out → cubic_in per "softer on the first ~5-6 hits."
- Kick: (sign(vx) * random_float(0, 4), -16) → (0, -10) per "gentler also vertically, and have no horizontal component."

**Documentation updates at end:**
- main.lua header rewritten to describe actual current state (was still labeled "v0 step 1: bare physics scaffold").
- design.md "What's already implemented" section rewritten to reflect the full physics scaffold + energy systems + squash polish, and explicitly list what's still not built (event bus, chips/mult, cards, weapons, projectiles, etc).

**Next steps identified:**
- Per design.md: event bus + chips/mult counters + first cards + single-round playtest. This is the architectural backbone the entire scoring layer depends on.
- Alternatives offered: round structure first, further polish, HUD cleanup. User was satisfied with current state and chose to end the session before picking a direction.

Approve and I'll proceed with transcript conversion + commit + push?

Yes.

Bash (python E:/a327ex/Anchor2/scripts/find-recent-session.py --limit 5)

2026-04-28T00:05:49.221Z 895f4d52-b748-4726-8d6b-678350a50bfe [claude] <-- MOST RECENT
   C:\Users\adn\.claude\projects\E--a327ex\895f4d52-b748-4726-8d6b-678350a50bfe.jsonl

2026-04-28T00:05:30.106Z b1236ad2-cb56-4906-a681-46014a7cf427 [claude]
   C:\Users\adn\.claude\projects\E--a327ex\b1236ad2-cb56-4906-a681-46014a7cf427.jsonl

2026-04-27T12:53:55.755Z 2630f741-c408-4a78-ac4a-c447ba958dbc [claude]
   C:\Users\adn\.claude\projects\E--a327ex\2630f741-c408-4a78-ac4a-c447ba958dbc.jsonl

2026-04-27T12:16:40.942Z c219fe18-809e-4000-be4a-fa5e224e8bba [claude]
   C:\Users\adn\.claude\projects\E--a327ex\c219fe18-809e-4000-be4a-fa5e224e8bba.jsonl

2026-04-27T03:01:08.340Z 8f867da8-6295-4e85-8aa6-d0f5774e6771 [claude]
   C:\Users\adn\.claude\projects\E--a327ex\8f867da8-6295-4e85-8aa6-d0f5774e6771.jsonl