Anchor Arena Test

Summary

Cursor session continuing Anchor2's arena/ test harness — a small twin-stick shooter used to validate the v2 framework against the real C engine. The work drove through ARENA_PROGRESS Steps 4–6, pulled visuals and feel from Orblike's seeker / fire_shots / projectile, and added a shared collection_update helper. By the end the arena has Orblike-aligned enemies, projectiles, hit FX, shoot juice, death burst, and a muzzle-offset spawn.

Orientation:

• Opened with "Let's continue on Anchor2. Get acquainted." — mapped the repo (engine/ C, framework/anchor/, arena/, reference/hello_world/, START_HERE.md, reference/progress.md).
• Noted arena/main.lua was already past the checklist in arena/ARENA_PROGRESS.md — Steps 2–3 (palette/layers/camera/background, Orblike-style player movement) were actually implemented; the doc still marked them open.

Step 4 — enemies spawn and chase:

• Added physics_register_tag('enemy') + physics_enable_collision('player', 'enemy').
• enemies = {}, spawn_timer = timer_new(), timer_every(spawn_timer, 1.5, 'spawn', spawn_enemy).
• First pass enemy class: 10×10 dynamic box, gravity 0, damping 3, steering_seek(p1.x, p1.y, speed, 200) + apply_force.
• random_edge_position() picks one of four edges with a small inset margin.
• Update loop: timer_update(spawn_timer, dt) then a reverse for + table.remove on _dead.
• Marked Steps 2–4 ✅ in ARENA_PROGRESS.md, note that movement uses set_velocity + axis decay (not input_vector + apply_force as originally sketched), Step 5 🟡.

User question on aggregate patterns:

• "Is this the default way in which updating a collection of entities should happen in Anchor2? There's no automation for it, not even the _dead check and so on?"
• Answered: yes — the framework registers entities in the global entities map via make_entity, kill() queues destruction, process_destroy_queue() sets _dead = true and clears the map, but typed groups (enemies, bullets) are always explicit game-owned arrays. The reverse loop + table.remove on _dead is the intended pattern.

Shared helper — aggregate.lua → helpers.lua / collection_update:

• First iteration wrote framework/anchor/aggregate.lua with aggregate_update(list, dt, method?) (reverse scan, drop _dead, call method default 'update') and aggregate_draw(list, method?) (forward scan, skip _dead, default 'draw').
• Wired it into framework/anchor/init.lua after object, synced arena/anchor/aggregate.lua, updated arena/main.lua and reference/hello_world/main.lua call sites.
• User pushback: "Don't call it aggregate, just helpers.lua and a collection_update function that does it. No need for draw since there's no complex code there."
• Renamed to framework/anchor/helpers.lua, deleted both aggregate.lua copies, kept only collection_update(list, dt, method?), reverted draws in arena + hello_world to plain for _, e in ipairs(...).

Orblike seeker alignment + camera fix:

• User: "Let's actually make sure that the enemies that are spawned now behave just like the Seekers from Orblike. In terms of both movement, collision against the player and so on. Also let's remove camera follow from player."
• Read Orblike seeker (main.lua ~9203–9514) and the player↔enemy begin-contact block (~12559–12585).
• Enemy now: 14×6 box, base_speed = random_float(50, 75), fixed rotation, damping 3, steering_seek + steering_wander(64, 32, 16, dt, speed, 200) + steering_separate(16, enemies, speed, 200), forces combined with math.limit(..., 200), velocity capped to self.speed via set_velocity, rotation lerps toward velocity heading with math.lerp_angle_dt(0.99, 0.1, dt, self.r, vel_r) while not pushed.
• enemy:push(r, force, duration) mirrors Orblike seeker:push: bump damping to 6, apply_impulse(force*cos/sin(r)), spin tween to 0, spring_pull('main', 0.3, 5, 0.5), brief flash, restore damping after duration.
• Spawn juice: spring_pull('main', 0.75, 3, 0.7) + 0.15s flash.
• Player: hp = 5, player:hit(damage) with spring + HP (later extended with hit point + FX).
• CONTACT_FORCE = 6. After updates, collision_entities_begin('player', 'enemy') → angle_to_point(player → enemy) → e:push(r, CONTACT_FORCE) + pl:hit(e.contact_damage or 1).
• Removed camera_follow(main_camera, p1); main_camera stays centered at (240, 135) for a fixed arena view.

Draw-error fix (attempt to call a number value):

• Runtime error main.lua:245: attempt to call a number value (local 'c') in enemy:draw.
• Root cause: fg_color() and enemy_color() in arena/anchor/color.lua are color tables with __call that return the packed RGBA integer, not a color object. Writing local c = self.flashing and fg_color() or enemy_color() made c a number; then c() tried to call the number.
• Fix: select the color object first, then call it once — local col = self.flashing and fg_color or enemy_color → col() in layer_rounded_rectangle. Same pattern used later for player and projectile draws.

Step 5 — projectiles (Orblike-style):

• User: "Let's actually make sure enemies physically hit each other — right now they go through each other" → added physics_enable_collision('enemy', 'enemy') so Box2D contacts kick in alongside steering_separate.
• physics_register_tag('projectile') + physics_enable_sensor('projectile', 'enemy') (hits are sensor, like Orblike physics_sensor('projectile', 'enemy')).
• First projectile pass: dynamic circle r4 { sensor = true }, set_bullet(true), speed 190 (Orblike default base_speed ~190), gravity 0, fixed rotation, velocity along aim, spawn spring_pull('main', 0.5) + 0.2s flash, lifetime 2.0.
• projectiles = {}, spawn_projectile(x, y, angle), collection_update(projectiles, dt).
• bind('shoot', 'mouse:1') — initial version used a manual shoot_cooldown counter inside player:update.
• Update loop: sensor_entities_begin('projectile', 'enemy') → e:hit(1) + proj:kill().
• enemy:hit(damage) with hp = 2, max_hp = 2, spring_pull('main', 0.5, 5, 0.5), 0.15s flash, kill() at 0 (later routed through enemy:die).
• Draw order: enemies → projectiles → player so shots read on top.

Timer-driven shoot — cooldown, trigger, edge detection:

• User: "We can use and also test one of the timer module functions to do this, I think timer_cooldown? Read the docs and try."
• Read framework/anchor/timer.lua: timer_cooldown(t, delay, condition_fn, 'name', callback) only fires when e.time >= delay AND condition true; on false→true it resets e.time = 0, so the first shot while held would otherwise wait a full SHOOT_INTERVAL.
• First attempt: timer_cooldown in player:new + an input_pressed('shoot') → player:shoot() branch in player:update for the immediate first shot. SHOOT_INTERVAL = 0.15 constant, player:shoot() extracted so press + cooldown share one implementation.
• User: "We should have a way to not need this. There's a way for timer functions to run immediately once I think."
• Switched to timer_when(t, cond, 'shoot_edge', fn) on input_down('shoot') false→true, calling timer_trigger(self.timer, 'shoot') — for mode 'cooldown', timer_trigger runs the callback once and resets e.time = 0 (see timer.lua ~241–256). Both registered in player:new. No input_pressed in update.
• User: "Isn't there a variant of cooldown that also does immediate calling of the action?"
• Answered: no — only timer_cooldown exists in Anchor2's timer.lua, and v1's docs agree. Composition via timer_trigger is the supported way; a first-class immediate = true option would be a small framework change.
• User: "We can just call timer_trigger then, but we have to do it only once it's pressed. Your initial solution was right then, I just don't like it being not local (in different places in the codebase)."
• Final layout: timer_cooldown(self.timer, SHOOT_INTERVAL, function() return input_down('shoot') end, 'shoot', function() self:shoot() end) registered in player:new, and immediately after timer_update(self.timer, dt) in player:update: if input_pressed('shoot') then timer_trigger(self.timer, 'shoot') end. All shoot timing stays in player:update next to timer_update. timer_when removed.

Step 6 check:

• User asked what Step 6 was — ARENA_PROGRESS.md says "Collisions and HP": player 5 HP, enemies 2 HP, collision_entities_begin('player','enemy') / sensor_entities_begin('bullet','enemy'), death via kill(), prove physics.lua + kill/process_destroy_queue end-to-end.
• Answered: most of Step 6 is already done; the doc still says bullet where the code uses projectile, and input_pressed('shoot') where the code now uses the cooldown+trigger pair — aligning names + marking done is what's left.

Orblike projectile size + hit FX (hit_circle / hit_particle):

• User: "Let's make sure projectiles are just like Orblike in terms of size, juice. Hit circle, hit particles and so on + juice on player should also be the same."
• Read Orblike hit_circle / hit_particle (~10465–10573), projectile spawn (~7822, ~7831–7834), sensor begin (~12597–12603), null_arrow particles (~8305–8308), player contact (~12577–12584, ~7310–7319).
• Projectile reshaped from circle r4 to Orblike default 10×4 sensor box; drawn as a rotated rounded rect radius 2 with col() (flashing → fg_color else bullet_color).
• Added effects = {} list, updated with collection_update(effects, dt), drawn after entities.
• hit_circle class: x, y, radius, draw_color, duration, timer_tween radius→0 with math.cubic_in_out, self:kill() at end. change_color(fraction, target_color) via timer_after at fraction * duration.
• hit_particle class: random velocity/angle/duration, w/h from math.remap(velocity, 100, 250, 7, 10), tween { w = 2, h = 2, velocity = 0 } with math.sine_in_out, motion along angle per dt, optional spin. Also change_color.
• color_clone used for per-instance colors so mutation is safe.
• Note: first iteration passed name strings to timer_tween ('hc', 'hp') — rewritten to positional timer_tween(self.timer, duration, self, {...}, ease, done) to match the function's actual signature; timer_after tags were suffixed with tostring(self.id) to keep them unique per entity.
• fx_projectile_hit_enemy(proj, e): impact point at e.x/y + 0.75*max(w,h) * cos/sin(angle_to_point(e,proj)), hit_circle r10 / 0.2s :change_color(0.5, enemy_color), 1–2 hit_particle velocity 50–150 with same color shift, shake_push(main_camera.shake, r + π, 4).
• player:hit(damage, hit_x, hit_y) now: spring_pull('hit', 0.2), 0.1s flash (flashing field + fg_color in draw), and when a hit point is present, hit_circle r6 / 0.15s + 1–2 particles vel 60–120 / 0.1–0.3s. Collision loop passes ev.x, ev.y with a player–enemy midpoint fallback for when the engine doesn't supply a contact point.

Shoot juice, enemy death, camera shake:

• User: "Improvements: death effect for enemy, hit circle + particles when player shooting effects, proper camera shake when shooting. Let's do these just like in Orblike."
• Read Orblike fire_shots (~2011–2056, ~2027–2044) and seeker:die (~9441–9459).
• player:shoot() now: shake_push(main_camera.shake, aim, 3) (same as camera.shake:push(r, 3), replaces the old aim + π / strength 2), spring_pull(self.spring, 'shoot', 0.25) (was 0.35), 0.15s flash via flashing + timer_after, and fx_player_muzzle(self.x, self.y, aim).
• fx_player_muzzle(sx, sy, aim_r): hit_circle r7 / 0.2s, 2× hit_particle with angle = aim_r ± π/4, velocity 40–200, duration 0.3–0.6, w ∈ {6,8} / h = w/2, :change_color(0.5, bullet_color).
• Initially added shake_shake(main_camera.shake, 3, 0.15) alongside shake_push, then removed it to stay faithful to Orblike's fire_shots, which only uses push(r, 3).
• enemy:hit now routes HP≤0 through new enemy:die() (Orblike seeker:die): spring_pull('main', 0.75), hit_circle r14 / 0.4s :change_color(0.6, enemy_color), 4–6 hit_particle velocity 100–300 / 0.2–0.5, :change_color(0.6, enemy_color), then self:kill().

Muzzle offset:

• User: "The position for the projectile + hit circles + particles needs to be offset from the player center a little."
• Added MUZZLE_OFFSET = 8 and in player:shoot(): mx = self.x + cos(aim) * MUZZLE_OFFSET, my = self.y + sin(aim) * MUZZLE_OFFSET. Both spawn_projectile(mx, my, aim) and fx_player_muzzle(mx, my, aim) use that point so the projectile body, muzzle hit_circle, and muzzle particles all line up ahead of the player along the aim ray.

Naming + session close:

• User: "Perfect, let's end the session here. Name it 'Anchor Arena Test'" — updated require('anchor') title to "Anchor Arena Test" (480×270, scale 3), reworded the file banner comment, and changed the print('arena: framework loaded OK') startup line to 'Anchor Arena Test: framework loaded OK'.
• User clarified: "I mean that you should load the end session skill and do the steps there." — end-session workflow began from the skill file in e:\a327ex\.claude\skills\end-session\skill.md (transcript → Markdown via jsonl-to-markdown.py, Blot log, context sync, git); in that run the log was named anchor2-arena-session-wrap.md by mistake, which this replacement corrects to anchor-arena-test.md.

Headless verification:

• arena\anchor.exe arena --headless --verify was run after each mechanical change (enemy step, aggregate/helpers rename, seeker alignment, projectile step, timer_cooldown refactor, FX + projectile reshape, death/shoot FX, muzzle offset) — every verify exited 0.

Let's continue on Anchor2. Get acquainted.

Opus 4.6

Anchor/
anchor.blot.im/
Anchor2/
Anchor-lua/
Anchor-YueScript/

arena/
docs/
engine/
framework/
reference/
scripts/
START_HERE.md

1    # Anchor 2 — Start Here
2   
3   If you're waking up and looking at this project, this is the entry point.
4   
5   ## What happened overnight
6   
7   The full Anchor 2 framework rewrite is complete. 18 files totaling ~4500 lines in `framework/anchor/`, replacing the v1 framework with:
8   
9   - **No object tree** — entities live in a flat `entities` table indexed by ID
10  - **No main-loop hook system** — `update(dt)` and `draw()` are game-level globals
11  - **No `an` god-object** — resources are plain globals (`layers`, `sounds`, `images`, etc.)
12  - **Mostly procedural framework modules** — `timer`, `spring`, `camera`, `shake`, `animation`, `physics` are procedural. `layer` and `collider` stay as classes.
13  - **ID discipline for cross-entity references** — `self.source_orb_id = orb.id` then resolve via `entities[self.source_orb_id]` when used
14  - **Deferred destruction** — `entity:kill()` queues, `process_destroy_queue()` finalizes at end of frame
15  
16  Every framework file parses clean. A stubbed integration test runs the hello-world game for one frame without errors. It has NOT been run against the real engine yet.
17  
18  ## What you should read, in order
19  
20  1. **`reference/progress.md`** — file-by-file status, totals, what's verified, what isn't
21  2. **`reference/questions_for_user.md`** — decisions I made during implementation that may need review
22  3. **`reference/hello_world/main.lua`** — canonical example of v2 game code style. Read this to see how v2 feels.
23  4. **`.claude/CLAUDE.md`** — the style guide for future instances, with a full code example
24  
25  If something in the plan changed during implementation, the change is documented in questions_for_user.md with reasoning. Read those answers before pushing back on any decision — I may have context you don't.
26  
27  ## How to actually run hello-world (untested)
28  
29  See the "How to run hello-world" section in `reference/progress.md`. Short version:
30  
... [55 more lines]

1    # Arena — Anchor 2 test game progress
2   
3   **Current task**: building `arena/`, a minimal twin-stick arena shooter, incrementally. Each step adds one small thing so the user can test as we go.
4   
5   **If you're a new instance picking this up**: read this file, then check the last ✅ step and continue from the first ⬜ step. DO NOT do multiple steps at once — user wants to test between each one.
6   
7   ---
8   
9   ## Context
10  
11  The Anchor 2 framework rewrite is complete (see `../START_HERE.md` and `../reference/progress.md` for that story). `arena/` is a test game that exercises every framework file. The goal is:
12  - Verify the framework works end-to-end against the real engine
13  - Provide a canonical code example for future Anchor 2 games
14  - Catch subtle bugs that the overnight stubbed integration test couldn't
15  
16  ## Philosophy
17  
18  - **Small steps.** Each step adds one thing and is independently runnable. After each step, the user tests it in a real window before I proceed.
19  - **Port juice from Orblike, not the OOP patterns.** Copy the feel of Orblike's hit effects, sounds, enemy AI, but translate to v2's procedural/ID-based style.
20  - **Use assets from framework/assets and Orblike/assets.** Already copied into `arena/assets/` (font, hit1 spritesheet, 7 sounds).
21  
22  ## Game design (target end state)
23  
24  Twin-stick arena shooter:
25  - **Player**: blue square, WASD to move, LMB to shoot toward mouse, 5 HP
26  - **Enemies**: red squares, spawn at edges every 1.5s, chase player via steering_seek, deal 1 damage on contact
27  - **Bullets**: yellow circles, sensor-triggered on enemies, 1 damage, destroy enemy on hit
28  - **HP / Score text**: top-left HP, top-right score, via font (LanaPixel.ttf)
29  - **Score popups**: "+10" text that tweens upward and fades (tests timer_tween)
30  - **Hit effects**: hit_circle + hit_particles on damage, hit_effect spritesheet on enemy death
... [152 more lines]

1    --[[
2     arena — Anchor 2 test game.
3   
4     Step 3: player movement. Movement feel matches Orblike (main.lua ~7248–7573):
5     - base_speed 100, 10x10 collider, gravity scale 0
6     - set_velocity from WASD (8-way), axis decay x0.8 when that axis has no input
7     - spring pull on 'move' when input stops
8     - aim rotation lerps toward mouse; optional Orblike spin/squash on left/right press
9   ]]
10  
11  require('anchor')({
12    width = 480,
13    height = 270,
14    title = "Anchor 2 arena",
15    scale = 3,
16    filter = "rough",
17  })
18  
19  print('arena: framework loaded OK')
20  
21  -- Palette
22  bg_color = color(20, 20, 28)
23  fg_color = color(220, 220, 220)
24  player_color = color(100, 150, 255)
25  enemy_color = color(220, 80, 80)
26  bullet_color = color(255, 220, 100)
27  
28  -- Physics: Orblike arena (no gravity)
29  physics_init()
30  physics_set_gravity(0, 0)
... [146 more lines]

Oriented. Anchor 2 is the Lua-framework rewrite (flat entities, no object tree, procedural modules, ID discipline). Framework rewrite is done; current work is arena/ — a twin-stick test game built incrementally.

State of arena: ARENA_PROGRESS.md still marks only Steps 0–1 as ✅, but arena/main.lua has already implemented Step 2 (palette, layers, camera, bg) and Step 3 (player class with collider, WASD movement, aim lerp, spring-pull on stop, direction-change spin/squash, camera follow). Step 3 looks complete in the code but isn't yet checked off in the progress file — which suggests it hasn't been confirmed by you in a real window run yet.

Before I touch anything, two questions:

1. Has Step 3 been tested in a windowed run and confirmed working? If yes, I'll tick Step 3 → ✅, mark Step 4 → 🟡, and start on enemies (spawn timer + steering_seek chase). If no, I should wait for you to test first.
2. Anything you want revisited in Step 3 before moving on (movement feel, squash/spin amount, camera follow lag)?