Snake · qwen3.8-max-0902

Let me build it and test it.

Key logic details: queue direction changes so that consecutive inputs don't reverse; compare against the last queued direction. Tail vacating is allowed: when moving into the tail cell, if it's not a growth step, no collision.

I'll write index.html.

There's a subtle issue with the win-determination logic. If spawnFood fails (i.e., the board is full) but snake.length is still less than GRID*GRID because grow hasn't been resolved yet... Actually, when food is eaten, the snake grows by 1 on this step (grow=1, popped off later). snake.length after unshift but before pop equals the final length. spawnFood computes the empty cells excluding the head at the new position, but the tail is still included in snake (even though it'll be popped). Edge case: when the snake fills the board except for one cell — eating the food in that cell, spawnFood detects that the tail cell is still occupied → returns false, but snake.length after unshift = GRID*GRID → win. This check handles it: `if(!spawnFood()){ if(snake.length>=GRID*GRID) win(); }`. But if the board is full except for the tail cell that gets vacated... snake.length would be GRID*GRID-1+1 = GRID*GRID → win. Correct. If spawnFood returns false but the length is less than GRID*GRID, food remains null — but that can only happen if the board is full, which means the length equals GRID*GRID. No problem.

Wait — there's one bug: when eating, we're doing both `grow += 1` and later `grow--` — this works: grow becomes 1, then gets decremented to 0, and pop is skipped. Correct.

Also, `willGrow = eating || grow>0` — but the eating case is handled separately. If grow>0 comes from a previous meal... grow gets decremented every step, so it can never exceed 1. No problem.

Alright, let's test it in the browser.

The initial state looks correct. Next, click Start and test the movement/turning.

The game has started, the snake is moving to the right, and the overlay is hidden. Next, test turning: press ArrowUp, then ArrowLeft (rapid consecutive input), and also test reversal prevention. Let's press the keys and take a screenshot.

The snake reached the wall before my ArrowUp arrived (the game had been running for a while between tool calls — about 10 cells to the right at 110ms/tick, plus the delay between calls). Wall collision is working correctly. Good.

Next, restart and test turning more quickly: start, immediately press ArrowUp, then ArrowLeft, and take a screenshot right away. The delay between browser calls is real time, and the snake moves about 9 cells/second. From the starting position (10,10), moving right reaches the wall (x=19) in 9 ticks ≈ 1 second. So the turn has to be executed immediately after starting.

Better approach: start, then within the same call... each browser call is separate. The interval between calls is probably several seconds. So the snake dies quickly. To test turning, start and immediately send ArrowUp in the next call — but the interval might exceed 1 second. Hmm, in the previous sequence: click Start (call), then key ArrowUp (call) — by that point the snake had already hit the wall. So the interval is more than about 1 second.

Options: slow the game down? No — better to test with a script via console? The browser tool doesn't have eval. But I can use the "motion" action to capture frames. Or, temporarily test the logic with node? The logic is simple, but the task requires browser verification.

Alternative: make the tick slower? 110ms is reasonable as gameplay. But for testability, I can start and then immediately press keys in consecutive calls. Risky.

Better approach: use keyboard operations with the motion action? The motion action captures frames over time.

Another approach: verify the turn logic with a headless test of the same logic in node? The requirement is to verify in the browser. I could also reduce the delay: start the game, then quickly send ArrowUp in the next call. The interval between the previous two calls was enough for the snake to travel 9+ cells (about 1 second). The snake starts at x=10 (head at x=10? cx=10). Wall at x=19: 9 steps ≈ 990ms. The interval between calls is probably 1-3 seconds.

Safer test: press ArrowUp immediately after start — but I can't guarantee timing. Alternative: first pause the game, then... turns are only accepted while running.

Hmm — but I can make the test deterministic: click Start and send ArrowUp in the same block? "If you intend to call multiple tools and there are no dependencies between the calls, make all independent calls in the same block." Click Start and key ArrowUp: the key depends on the start having happened, but both are sequential operations on the same page; if executed in order within one block, they'll run in order. The instructions say dependent calls must wait. But these are effectively ordered UI events; the result of the second depends on the first, but I know the first will succeed (the click coordinates are known). I think sending both in one block is acceptable — they'll execute in order.

Next, in the same block, ArrowLeft (rapid consecutive input: up followed by left is a valid turn, not a reversal). Then screenshot.

Sequence: start at (10,10) facing right. Tick 1: apply queued direction? Queue: [up, left]. Step 1: dir=up, head (10,9). Step 2: dir=left, head (9,9). Subsequent steps continue left. Screenshot should show an L-shaped path... but the snake is length 3; the shape shows the current segments: after 3+ steps, segments: (8,9),(9,9),(10,9)? Then continuing left. The screenshot shows a horizontal row at y=9. Hmm, to visually confirm the turn, take a screenshot after a few steps: the snake is moving left along row 9.

Also test reversal: while moving left, quickly press ArrowRight then ArrowUp: right is a reversal of left → ignored; up is valid. If reversal blocking works, the snake turns up.

Also test tail-chasing: hard to set up quickly; trust the logic.

And eating: hard to guarantee. Maybe I can steer toward the food... the food position is random. Alternative: verify score increment via a longer scripted run? Difficult.

Maybe I can verify eating deterministically: food position is visible in the screenshot. The snake starts at (10,10) facing right. If the food is on row 10 to the right of the head, it'll be eaten automatically. Otherwise steer.

Plan: one block: click Start, key ArrowUp... but wait: at start, dir=right; pressing up is valid. Then left. Then screenshot in the next block (1+ second later, snake moving left, probably still alive; from (10,10): after up+left, moving left from x=9; wall at x=0: 10 steps ≈ 1.1 seconds. Screenshot might catch it near the wall or dead. Hmm.

Instead let's do this: start, ArrowUp, ArrowUp? Duplicate ignored. Start, ArrowUp, then ArrowRight? After up, right is valid (not a reversal). Then the snake goes up column 10, then right along some row... wall on the right again.

Simplest deterministic visual: start, ArrowUp (turn up), screenshot about 0.5-1 second later: snake moving vertically up column 10/11. Then ArrowLeft, screenshot: moving left. Each screenshot call also takes time; the snake might die at the top wall (from y=10 to y=0: 10 steps ≈ 1.1 seconds). Ugh, 110ms ticks are fast relative to tool latency.

Consider raising TICK_MS to about 140ms — still snappy. 10 steps = 1.4 seconds. Tool latency unknown; the previous interval allowed 9+ steps between two calls, so latency ≥ about 1 second, probably more.

Alternative robust approach: pause-based inspection. Turns are only accepted while running. But I can pause and take a screenshot of the frozen state! Sequence: start → ArrowUp → (latency) → ArrowLeft → pause (Space) → screenshot shows the frozen snake shape revealing the turns. But if the snake dies during the latency, pause does nothing.

Mitigation: choose turns that keep the snake in the center: start facing right; press ArrowUp early (within the first latency window, snake at about x=10-15, y=10); then during the second latency it moves up from y=10 to y=0 → dies at the top wall within about 1.1 seconds. Hmm.

Use a longer path: start facing right; immediately press ArrowDown? Same problem in reverse.

OK, alternative: temporarily instrument via URL? Not allowed? I can add a debug hook: expose window.__snake for testing? That's fine — a small debug handle is harmless. But better: make the game testable by allowing a slower speed? Not in the spec.

Realistic approach: accept some flakiness; retry the sequence a few times. Or reduce latency impact: send multiple key events and a pause in one block: click Start, key ArrowUp, key ArrowLeft, key Space (pause). All within one block, executed in order with minimal delay between them. Result: snake: step? The interval between events within a block is probably milliseconds, so the queue: up, left; pause immediately → state paused before any step? Then the queue remains; resume later to see the turns. Then screenshot shows the paused overlay with the snake still horizontal. Then click Resume, wait, screenshot: snake should be moving left along row 9 (after up,left applied). Hmm, but between resume and screenshot (about 1+ second), moving left from (10,9): 10 steps to the wall → might die before the screenshot.

Instead, queue turns that keep it near the center: start facing right at (10,10). Queue: up, left, down? Up: (10,9); left: (9,9); down: (9,10); then continue down to wall y=19: 9 steps. Screenshot after about 1 second: snake vertical around (9,14-19)... might be dead.

Honestly, wall death is also verification of boundary behavior. For turn verification, the paused screenshot approach: pause freezes exactly the state after the queued turns are partially applied... turns are applied on step; while paused, no steps. So queue up, left and pause immediately → zero steps, snake unchanged. Not useful.

New idea: use the motion action! "motion" captures frames over time. Maybe I can start and then capture motion frames showing the snake's movement and turns. But turns still require key events during capture.

Simplest: expose a small test hook. Add `window.__snakeTest = {get state(){...}}`? The task says verify with the browser tool; using a console hook via... the browser tool has no eval action. Actions: reload, inspect, screenshot, motion, click, drag, key, type, scroll. No JS eval. inspect returns DOM/console.

Hmm, but I can read state from the DOM: score element, overlay text. Snake position isn't in the DOM. Screenshot shows the canvas.

Plan with retries: Block A: click Start; key ArrowUp. Block B (right after): screenshot. If dead at wall, retry with a different sequence. Latency between A and B about 1 second: snake: at some tick up is applied... in block A, click then key: snake may have advanced 0-2 cells. Then up applied on next tick. Between A and B (about 1 second ≈ 9 ticks): snake moves up 9 cells from y=10 → y≈1, alive or dead at top (needs 10 steps). Borderline.

Slow the game slightly: TICK_MS=150. 9 ticks=1.35 seconds... latency unknown.

Alternative: make the board traversal longer: snake starts in the center; no problem.

Maybe better: verify turns via pause screenshot: Block A: click Start, key ArrowUp, key Space (pause). If pause lands before the first tick (likely if intra-block latency is ms and tick is 110ms), snake frozen at start position with dir queue [up]. Screenshot shows the paused overlay + horizontal snake. Then Block B: click Resume; key... hmm.

Actually the simplest, most robust verification of turn + grid alignment: capture motion frames right after start with a turn queued. motion action: probably captures N frames over a period. If I queue ArrowUp right after start (block A: click Start, key ArrowUp), then immediately call motion (block B): motion frames over about 1-2 seconds show the snake moving right then curving up — grid-aligned movement and turn visible across frames. Even if it dies at the top at the end, the frames show the turn.

Let me check what motion returns. Try it: Block A: click Start + key ArrowUp. Block B: motion.

Then for rapid-input reversal test: Block C: click Restart? Restart returns to idle. Then Start, queue: ArrowLeft (reversal of right → ignored), ArrowUp (valid), then motion/screenshot: snake should turn up, not left. If reversal weren't blocked, the snake would... left is a reversal → if buggy, immediate neck collision death. So survival + upward movement proves blocking.

Rapid consecutive: