Snake · kimi-k3

Let me write the index.html file with a complete Snake game.

Initial render looks good. Now start the game, make turns, pause, resume, restart. Click Start button at (506, 637). Then press arrow keys. Use motion to check movement. Let me click Start then press ArrowDown.

Game is running, snake moved right. Now make turns: press ArrowDown, then ArrowRight, then ArrowUp quickly, observe.

The snake hit the right wall before I pressed ArrowDown (time passed between the click and key press — the snake went straight right into the wall). Game over state shown correctly, including wall collision. That's actually a valid verification of wall collision and game-over.

Let me restart and press an arrow key immediately. Restart resets then starts running. I'll click Restart then quickly press ArrowDown.

Restarted: score 0, length 3, snake back at start position, food in a new free cell. Good — restart reset works. Now it's running; press ArrowDown immediately.

There seems to be a significant delay between tool calls (the snake traveled ~11 cells to the right wall at 130ms per tick — that's ~1.5s of real time between my restart click and key press). The game logic itself appears fine; the tool round-trip is slow. I'll use motion to capture frames, or better: send the key and check whether the turn took effect. Alternatively use motion with a key? The motion tool captures motion frames — but actions are separate.

Better approach: verify turn behavior by pressing a key immediately after restart in the same observation. Since round-trip delays exceed tick time, I can't reliably test turns interactively this way. But I can verify turn responsiveness: restart, then in one key action press... hmm, key action takes one key.

Alternative: I can test turning by pressing ArrowDown while the game is at "Game Over" — no. Let me instead test via pause: restart → key Down quickly still has delay.

Actually, I can verify direction handling by driving the game deterministically — e.g., temporarily testing in node? Or just rely on code review for turn logic and use browser for pause/resume/restart states. But better: try pressing key and immediately taking screenshot — the key action itself returns a frame. If the round trip is ~1.5-2s, the snake moves ~12 cells. From start x=5 moving right, reaches wall at x=20 in 15 ticks ≈ 2s. So pressing Down after restart has ~2s window before wall death. The previous attempt died — snake at wall again, so round trip exceeded ~2s.

Trick: make snake survive longer by pressing ArrowDown — if the key registers before the wall, snake turns and lives much longer. The screenshot after keypress would show a snake heading down near the right side. In the last attempt, the snake was at the wall horizontally — the Down key never registered before death? Actually the frame shows snake horizontal at wall — meaning ArrowDown arrived after game over (ignored).

Hmm, maybe key events don't repeat fast. Let me try a different approach: use motion tool? Not helpful.

Alternative: slow the game down? No — don't modify the required behavior... Actually I could test with a longer-lived path: press ArrowUp instead — same issue.

Better: use the key action immediately followed by reading — but each tool call has latency. The key press happens in the browser when the action executes; the latency between click and key is the model+tool round trip, which I can't control.

Option: Press ArrowDown twice? Once game is over, keys are ignored except state idle.

Alternative robust test: restart via click, then the next key press — I'll try ArrowUp and hope the round trip is faster this time. If it keeps failing, I'll verify turn logic via code inspection and use a temporary console-based test? No console exec tool available.

Actually — I could test deterministically by injecting a small automated self-test into the page temporarily (query param), but no external modifications... It's fine: I can add a hidden self-test harness? That complicates. 

Simpler: use drag or type? "type" sends text — maybe faster round trip? Same latency.

Let me just try again: click Restart then key ArrowDown. Round trips vary. Actually, maybe I can make the turn test more forgiving: after restart, snake moves right; Down is a valid turn for the first 14 ticks (~1.9s). Try again.

The tool round trip is consistently slower than the ~2s window. To test turning deterministically, I'll verify the game logic headlessly with node by simulating the game code (extracting logic). But the game code is embedded in HTML with DOM dependencies.

Alternative: temporarily slow the tick for testing? That modifies the artifact. Instead, I can verify turn logic with a small node simulation replicating the logic — but that only tests my copy, not the page.

Better approach: I can make the browser test work by pausing! Click Restart (starts running), then click Pause — round trip may again exceed... pausing just freezes state; then while paused, queue a direction (queueDirection ignores input while paused — it returns if state !== "running" — hmm, my code ignores direction input when paused. Actually queueDirection checks state === "idle" → start; if state !== "running" return. So pressing arrow while paused does nothing).

Better: change approach — verify the turn logic by adding a tiny debug hook? No; keep the artifact clean.

Alternative: use node to run the game logic with a mocked DOM. That actually tests the real code in index.html. Let me extract the script and run it in node with stubs for document/canvas. That's feasible: stub document.getElementById returning objects with needed props, canvas getContext returning stub with methods, document.addEventListener capture keydown handler, setInterval/clearInterval exist in node. Math.random fine.

Then simulate: dispatch keydown ArrowDown, manually step... but step is driven by setInterval; in node I can use real timers and wait, or better override setInterval to capture callback and call manually. Since I stub the environment before evaluating the script, I control it.

Let me write a test harness: read index.html, extract script content, create sandbox with vm module.

Plan:
- fake elements: scoreEl etc. with textContent, classList {add, remove}, disabled, addEventListener noop.
- canvas: width/height 400, getContext returns proxy noop functions and settable props.
- document: getElementById map, addEventListener stores keydown handler.
- window not needed (script uses document, setInterval, clearInterval, Math).
- Override setInterval to capture fn and return id without scheduling; then test calls captured tick manually.

Tests:
1. Initial: snake length 3 (lengthEl.textContent == 3), score 0.
2. Press Start button handler → startBtn click listener captured. Then keydown ArrowDown (preventDefault captured) → queue. Call tick once: snake should have turned down — head y increased. Check via... internal state not exposed. I can infer from drawing? The draw function uses ctx.fillRect calls — I can record fillRect positions to reconstruct the snake! ctx stub records fillStyle + rect coords. Snake drawn with fillRect at x*CELL+1. Food drawn with arc. So I can parse positions.

Test sequence:
- Start.
- keydown ArrowDown, tick → head moved down (y+1).
- keydown ArrowUp (reverse) → should be ignored: tick → head continues down.
- Rapid: keydown ArrowLeft then ArrowDown before tick while moving down: queue base logic: base=dir(down); Left queued; then Down: base=last queued (Left); Down vs Left — not reverse, not same → queued. Tick1 → left, tick2 → down. Fine, that's intended (not reversing into neck).
- Reverse-into-neck rapid case: moving right, press Up then Left before tick. base for Left = Up (last queued) → Left is reverse of right? Left vs Up: not reverse, so queued. Tick: dir=Up. Then tick: dir=Left. Snake goes up then left — not into neck since it turned up first. Correct behavior.
- The prohibited case: moving right, press Left → ignored (reverse of dir). Press Left then Right: Left ignored, Right same → ignored. Good.
- Eating: place food in front... food is random. To test eating deterministically, I can stub Math.random to control free-cell selection. placeFood picks free[Math.floor(rand*len)]. With rand=0 → first free cell (scan order y,x). After reset, snake occupies (3,10),(4,10),(5,10). First free = (0,0). I can then drive snake to (0,0): from (5,10) moving right... path: up to (5,0)? Simpler: turn up ×10... just script the moves: Up (10 ticks), Left (5 ticks) → head at (0,0) eats → score 1, length 4.
  Wait head starts (5,10) after reset, first tick moves right to (6,10). Sequence: tick once (6,10), key Up, tick → (6,9)... need to reach (0,0): up 9 more times → (6,0), then left 6 times → (0,0). Total fine.
  After eating, score should be 1, length 4. New food placed with rand=0 again → first free cell now: snake occupies (0,0),(1,0)...,(0,? ) hmm snake body after path: head (0,0) plus trailing along the path. First free in scan = (7,0)? Snake at row 0 occupies x=0..6, and column x=6 y=0..10ish. First free cell scanning y=0: x=7 → (7,0). Food at (7,0) — directly in front? Head at (0,0) moving left. Next tick head → (-1,0) wall → game over. Fine, or turn down first.
- Wall collision: verified already in browser.
- Tail-vacate rule: construct scenario... harder to drive randomly. I could test via logic: make snake of length 4 loop: e.g., positions head (5,10), body (4,10),(3,10),(3,9)? Can't set directly. Drive: start (5,10) dir right. Moves: Down, Left, Up, Right → snake chases tail. After forming loop, moving right into tail cell... Let's simulate: length 3 initially; grow once to length 4? Tail-vacate check matters when moving into current tail position. With length 3: after loop, head at (4,9)? Let me not overcomplicate; I'll trust code review for tail rule: limit = eating ? len : len-1 — tail excluded from collision when not growing. Correct.

Also test pause: keydown space → togglePause, ticks do nothing (timer stopped — in my harness, tick only called manually, so pause just check state via pauseBtn text "Resume").
Restart: click restart → score 0, length 3, state running.

Let me write the harness.

Failures to analyze:

1. "new food in unoccupied cell" — my test's foodCell() reads arcs[0], but arcs accumulate across draws (never cleared). foodCell should use the LAST arc. arcs is never reset between draws! Same for rects — snakeCells() accumulates across all draws. That's why many later checks failed: stale data. I need to clear rects/arcs per draw. The draw() function calls clearRect — I can hook clearRect to reset rects/arcs... but food arc comes after clearRect in same draw. clearRect is called at start of draw. So reset rects/arcs in clearRect. 

2. "still alive after tight loop" — probably also artifact of stale rects, or actual death. Also "paused label" fail — hmm, pauseBtn.textContent — after game over? No, pause happens before wall death. Wait, paused label fail: after pauseBtn.click(), textContent should be "Resume". updateHud sets pauseBtn.textContent = state==="paused" ? "Resume":"Pause". Should pass... unless state wasn't running — maybe snake died during the loop navigation (hit body), making state "over", then pauseBtn disabled and click does nothing (togglePause returns since state not running/paused). Then "resume label" check: pauseBtn.click() again → textContent remains "Pause" → passed coincidentally. And "game over on wall hit" passed because it was already game over.

So possibly the snake DID die in the loop navigation. Let's debug: after fixing the rect/arc accumulation, re-run and see. Also verify my navigation path doesn't actually collide with body — with the deterministic food at (0,0) eaten, new food placed at first free cell with rand=0 → (7,0)? Snake after eating: head (0,0), body (1,0),(2,0),(3,0)? Wait path: up col 5 from (5,12) to (5,0), left to (0,0). Length 4: head (0,0), (1,0),(2,0),(3,0). Free first cell: scanning y=0: x=0..3 occupied, x=4? After ticks, the tail moved... complicated. New food at (4,0) maybe. Then my loop path: down to (0,1), right x4 to (4,1), up to (4,0) — if food is at (4,0), the snake EATS there! score becomes 2, length 5 → "score unchanged" fails and subsequent tail positions shift. Yes, that's likely. Also eating at (4,0) means growth... then left to (3,0): is (3,0) body? Snake at that moment: head (4,0), body (3,1),(2,1),(1,1),(0,1)? Hmm after eating length 5: head (4,0), (4,1)? no wait head came from (4,1) moving up to (4,0). Body: (4,1),(3,1),(2,1),(1,1),(0,1) minus tail... length 5: (4,1),(3,1),(2,1),(1,1),(0,1)? That's 5 body + head = 6. Hmm length was 5 after eat: head + 4 body: (4,1),(3,1),(2,1),(1,1). Then left to (3,0): free. down to (3,1): body! (3,1) is in body (index 1). Tail-vacate: tail is (1,1), doesn't vacate (3,1) → collision → game over. That explains it.

So my test navigation is flawed, not necessarily the game. Fix test: make rand return a value that places food elsewhere, e.g., rand = 0.999 (last free cell) after eating, or just navigate avoiding. Simpler: after the eat test, set randValues = [0.99] so new food goes to last free cell (bottom-right area), away from my loop path.

Also fix rect/arc clearing via clearRect hook.

Also for "still alive after tight loop" — redesign loop path accounting for snake geometry. Let me recompute with food far away. After eating at (0,0), head (0,0) dir left, length 4: body (1,0),(2,0),(3,0). New food at last free cell (19,19) with rand 0.999.

Moves: Down → (0,1). body: (0,0),(1,0),(2,0). Right x4 → (4,1). body after 4 rights: let's track: after R1 (1,1): body (0,1),(0,0),(1,0). R2 (2,1): (1,1),(0,1),(0,0). R3 (3,1): (2,1),(1,1),(0,1). R4 (4,1): (3,1),(2,1),(1,1). Up → (4,0): body (4,1),(3,1),(2,1). Left → (3,0): free? body (4,0),(4,1),(3,1). yes free. Down → (3,1): currently body index 2 (tail is (4,1))? body now: (3,0),(4,0),(4,1). (3,1) free. Down again → (3,2) free. Left → (2,2)? Let me make an actual tail-vacate test: move head into the cell the tail currently occupies.

Tail is the last body segment. Set up: snake length 4 in a small loop. From state head (3,0), body (4,0),(4,1)... hmm let me just do: Down to (3,1): body (3,0),(4,0),(4,1) → (3,1) is free ✓. Now head (3,1), body (3,0),(4,0),(4,1)?? wait after moving down to (3,1): snake: (3,1),(3,0),(4,0),(4,1). Tail (4,1). Move Right → (4,1) is tail cell, non-growing → allowed! Then snake: (4,1),(3,1),(3,0),(4,0). That's the tail-vacate test. Then next Right? dir right... continue Up → (4,0): body (4,1),(3,1),(3,0) → free ✓. Left → (3,0): body (4,0),(4,1),(3,1) → free ✓. Good loop.

So after the Down at (3,1), do Right (tail cell) and check alive. 

Then pause test, then wall: from (3,0) moving left... after loop moves end: Up (4,0), Left (3,0) moving left. Press... for wall test just continue left: ticks → (2,0),(1,0),(0,0),(-1,0) wall → game over. But careful: body collision en route? body (4,0),(4,1),(3,1); moving left along row 0 from (3,0): (2,0) free, (1,0), (0,0), then wall. 

Let me rewrite test sections accordingly. Also rand for second food: after eating at (0,0), snake occupies row0 x0-3 plus col5 trail? Length 4 — body (1,0),(2,0),(3,0) only (col5 trail gone). Free cells scan with rand 0.999 → last free = (19,19). Good, far away.

Also fix "new food in unoccupied cell" check — should pass with clearing fix.

Restart food check: reset uses rand again — randValues [0.999]?? I set randValues=[0.999] mid-test; reset → food at (19,19). Snake at rows 10. Free ✓.

Update test.js.

"setup alive" fails — snake died during the loop setup. Let me debug: print head/body and food after each move. Let me trace: after eating at (0,0), head (0,0), dir left, len 4: body (1,0),(2,0),(3,0). Food at last free cell. Which is last free? Scan y,x — last free = (19,19) unless occupied. OK.

Down → (0,1): body (0,0),(1,0),(2,0). Right x4: (1,1),(2,1),(3,1),(4,1) — wait, does it pass food at (19,19)? No. Up → (4,0): check body: after R4, snake: (4,1),(3,1),(2,1),(1,1). Up to (4,0): free ✓. body now (4,1),(3,1),(2,1). Left → (3,0): free ✓. Down → (3,1): body after left: (3,0),(4,0),(4,1). (3,1) free ✓. Tail now (4,1) ✓.

Hmm, but wait — when did it die? Maybe during Right x4: after Down to (0,1), snake (0,1),(0,0),(1,0),(2,0). R1 → (1,1): body (0,1),(0,0),(1,0). R2 → (2,1): (1,1),(0,1),(0,0). R3 → (3,1): (2,1),(1,1),(0,1). R4 → (4,1): (3,1),(2,1),(1,1). All free ✓.

Hmm, but wait — eating check: food at (19,19), no. What about the "Up" to (4,0)... fine.

Maybe the problem: key("ArrowDown") from dir=left — fine. But my earlier sequence before this: after the eat, dir is LEFT and head at (0,0). key("ArrowDown") then tickFn → (0,1). OK.

Let me add debug output to see where death occurs.

The snake died during the "up 12" navigation — head at (4,2) moving up, length 3. Why? Path: after the earlier rapid test, head at (5,12) moving left. Then key("ArrowUp") + 12 ticks: up from (5,12)... but head shows (4,2) — x=4! So it moved left first: tick order — after "rapid" test, head (5,12) dir left. I pressed ArrowUp then ticked 12 times. But queue: ArrowUp queued; tick1: dir=up, head (5,11)... head would stay x=5. But head x=4.

Ah — during the rapid test, I pressed ArrowUp (ignored) and ArrowLeft (queued), then ticked ONCE → head (5,12), dir left. Then key("ArrowUp") — queue base = dir (left), Up is fine, queued. tick: (5,11). continue up... x stays 5. But actual shows x=4. Hmm.

Wait — earlier sequence: key ArrowDown from start. Actually start: head (5,10) dir right. tickFn → (6,10). key Down, tick → (6,11). key Up (ignored), tick → (6,12). Then rapid test: key Up (ignored — reverse of down), key Left (queued), tick → (5,12) dir left. Then key Up, 12 ticks: (5,11)...(5,0), then 2 extra ticks? 12 ticks from (5,12): (5,11),(5,10),...,(5,0) = 12 ticks exactly. Then key Left, 5 ticks: (4,0),(3,0),(2,0),(1,0),(0,0) → eat at tick 5? (0,0) reached on 5th tick. But shown head (4,2)?! 

Hmm, length 3 and head (4,2) with Game Over. Something else: queue max 2 — during "for 12 ticks" I only pressed Up once. Fine.

Wait — maybe the earlier presses: my dbg shows "after eat" state Game Over with score... the snake died somewhere. Length 3 means it never ate. Head (4,2) moving up with body (4,1),(4,0)?? Body below head while moving up — that means it just turned. (4,2),(4,1),(4,0): head at (4,2), body above. It died moving up into... something at (4,1)? No wait, dead snake drawn is the position at death (before the fatal move). Head (4,2), body (4,1),(4,0) — vertical line. Death: moving up from (4,2) into (4,1) = own body! 

How did we get x=4? In the rapid test I pressed Up then Left. Up ignored (reverse of down), Left queued → tick → head (5,12) dir LEFT. Then key("ArrowUp") → base=dir(left) → queued. tick → (5,11)?? dir=up. Hmm x=5 still.

Wait, but in dbg I did: key("ArrowDown");tickFn() at the very start (after start). tick1: start→(6,10)?? No wait: els.startBtn.click() then key("ArrowDown") then tickFn() — ONE tick. dir queue [down], tick → dir=down, head (5,10)→(5,11)! Because in dbg I didn't do the initial right tick. Head (5,11) dir down. Then key Up (ignored), key Left (queued), tick → (4,11) dir left. Then key Up, 12 ticks: (4,10)...(4,-1)?? 12 ticks from (4,11): (4,10)...(4,0) is 11 ticks, 12th tick → y=-1 wall → game over! But shown head (4,2) len 3 died at body collision, not wall... hmm (4,1),(4,0) body means it moved down first? 

Ugh, whatever — the discrepancy is because dbg/test sequences differ from my mental model. In test.js the actual sequence: start, tick (6,10). key Down, tick → (6,11). key Up, tick → (6,12) [reverse ignored]. rapid: Up ignored, Left queued, tick → (5,12). key Up, 12 ticks → (5,11)...(5,0). key Left, 5 ticks → (4,0),(3,0),(2,0),(1,0),(0,0). Eat at (0,0) on 5th tick ✓. That passed in test.js! ("score incremented" PASS, "length grew" PASS).

So in test.js, after eat: head (0,0), dir left, len 4, body (1,0),(2,0),(3,0). Food now placed: randValues=[0.999] set AFTER eat — but food was placed during the eat tick using OLD rand sequence [0,0,...] → food back at first free cell! First free cell scanning y=0: x=0..3 occupied by snake → x=4 → (4,0)?? Wait also col 5 trail? Length is 4 so no. Hmm but wait: (5,0)? The body path up col 5 — tail trimmed. Len 4: (0,0),(1,0),(2,0),(3,0). First free in scan order: y=0 row: x=0-3 taken, x=4 free → food (4,0).

Then my loop: Down (0,1), Right×4 → (4,1), Up → (4,0) = FOOD! Eats → len 5, score 2. Then Left → (3,0): body now? After eat at (4,0): snake (4,0),(4,1),(3,1),(2,1),(1,1) len5. Left → (3,0) free. Down → (3,1): body (3,0),(4,0),(4,1),(3,1)?? wait after left: (3,0),(4,0),(4,1),(3,1),(2,1). Down → (3,1) is body index 3, tail is (2,1) → not vacating → COLLISION → game over. "setup alive" FAIL explained. It's the test path's fault (food at (4,0) in the way).

Fix: set randValues=[0.999] BEFORE the eating tick so the replacement food goes to (19,19). In test.js, move randValues assignment before "key ArrowLeft; 5 ticks" — actually before the eat occurs. Let me edit test.js: set randValues=[0.999]; randIdx=0; right before the final approach (before the 5 left ticks).

All 23 pass. Clean up test files? Keep test.js maybe — instructions say end with index.html present; extra files fine but I'll remove debug file. Keep test.js as evidence? I'll remove dbg.js, keep test.js (harmless). Then final browser check: reload and confirm initial state renders, and confirm pause button works in browser quickly (click Start then Pause — pause freezes before wall since it just needs one click within ~2s... pause click round trip might exceed but the state will show paused or game over). Quick final reload + screenshot is enough.