Maze generator & solver · mimo-v2.6-pro

Let me build the app. Single index.html, canvas maze generator (recursive backtracking), animated generation, BFS/A* solver animation, path highlight, buttons, legend.

Let me write it carefully.

Design:
- Canvas sized to fit, cell size computed.
- Maze grid 25 cols x 15 rows.
- Walls: each cell has walls [top, right, bottom, left].
- Generation: iterative recursive backtracking with stack, animated via requestAnimationFrame stepping N cells per frame.
- Cancelation: token/generation id.
- Solver: BFS (or A*). I'll implement A* with Manhattan heuristic but BFS is simpler and guaranteed. Requirement says "either BFS or A-star". I'll do BFS for simplicity... maybe A* is nicer. I'll do A* — actually BFS exploration looks nicer (wavefront). Let's do BFS, simplest correct. But "animate either BFS or A-star" — BFS fine.

Actually maybe implement A* to show off. Keep it simple and robust: BFS.

Animation state machine: 'generating' | 'solving' | 'path' | 'idle'.

Drawing:
- Background: light cells.
- Walls: dark strokes.
- Explored cells: light blue/green tint.
- Frontier (queue) maybe.
- Current exploring cell: orange.
- Path: red/blue thick line through cell centers.
- Start: green with "S", Finish: red/magenta with "F".

Legend: HTML div with swatches.

Controls: New Maze, Replay Solver. Maybe also speed slider (optional).

Cancelation: New Maze stops current animation (generation or solving), resets, starts fresh generation.

Replay Solver: only enabled after generation done; keeps walls; restarts solver animation from scratch (clear exploration and path).

Implementation details:

Data: cells = array of {walls:[t,r,b,l], visited}. Passages determined by removing walls.

Solving needs open passages: from cell to neighbor if wall between is absent.

Animation loop: use requestAnimationFrame with per-frame work counts, e.g. carve ~1 cell per frame at 60fps for 375 cells -> 6+ seconds. Maybe 2 steps per frame -> ~3s. Let's do speed control: generation steps per frame 2 (approx 3s). Solver: 3 cells per frame.

Better: time-based: accumulate elapsed time, do steps at fixed rate.

Let me write code.

Canvas size: container width up to 1100; cell size = floor(min((width)/25, ...)). Use devicePixelRatio for crispness. Let's set canvas width = 25*cellPx, height = 15*cellPx, cellPx maybe 32 -> 800x480. Plus a bit of margin for walls.

I'll compute cellSize from available width: clamp between 20 and 40.

Drawing walls: for each cell draw its top and left walls, plus outer right/bottom. Or draw all walls per cell (duplicates fine but lines doubled — with same color fine). Simpler: draw each cell's walls where wall exists; overlapping lines are fine.

Path drawing: polyline through cell centers of solution path, with lineWidth = cellSize*0.32, round caps/joins.

Let's write.

```js
const COLS=25, ROWS=15;
```

Generation algorithm (iterative):

```js
function* carveGenerator(){ ... }
```
Use arrays: stack of indices. Steps function returns true when done.

```js
function generationStep(){
  if (genStack.length===0) return true; // done
  const cur = genStack[genStack.length-1];
  const neighbors = unvisitedNeighbors(cur);
  if (neighbors.length===0){ genStack.pop(); return genStack.length===0; }
  const [nxt, dir] = neighbors[rand];
  removeWall(cur,nxt,dir);
  visited[nxt]=true;
  genStack.push(nxt);
  return false;
}
```
Start: visited[start]=true; genStack=[start].

For animation visibility, draw the stack as "current carve path" tint (like recursion stack) — nice: highlight stack cells in a warm tone. And also draw the most recent carved cell.

BFS:

```js
function solverStep(){ ... }
```
BFS with queue and visited set, parent pointers. Each step dequeues one cell, explores neighbors; when finish reached, reconstruct path and finish.

Animation loop:

```js
function tick(ts){
  if (state==='generating'){ do N generation steps with time accumulation; draw; }
  ...
}
```

Cancelation: keep `runId` increment; `requestAnimationFrame` loop checks a `running` flag; newMaze sets flags.

Simplest: single rAF loop that always runs (continuous) and dispatches based on state. That avoids cancel complexity: New Maze just resets state to 'generating' with new data. But requirement "New Maze cancels the previous animation and generates a fresh maze" — resetting state does that.

But rAF loop always running is fine and cheap (draw only when dirty). I'll do: loop always runs; if state generating/solving, perform steps based on elapsed; draw when changed.

Speed: use accumulator: stepsAcc += dt * rate; while stepsAcc>=1 do step.

Generation rate ~ 90 cells/sec -> 375 cells but with backtracking pops maybe ~700 steps -> ~8s. Hmm too slow. Let's do 140 steps/sec -> ~5s. Actually the verification wants to see carving progress, so ~4-5s is good. Solver BFS visits up to 375 cells at 120/sec -> 3s.

Let me set: generation 150 steps/s, solver 140 steps/s. Add a speed select? Keep a small speed multiplier select (0.5x, 1x, 2x) — optional, fine.

Path reveal animation: after BFS done, animate path drawing progressively (path reveal steps) — nice. Do it: pathProgress increases at rate, drawing partial polyline.

Legend items: Start (green), Finish (red), Explored (light blue), Frontier/Current (orange), Solution (blue line), Wall.

Status text: "Generating…", "Solving…", "Solved in N steps, path length M", "Maze ready".

Also handle "Replay Solver" when state is generating: disabled (or ignore). Requirement: New Maze cancels previous animation. Replay Solver uses existing maze without changing walls — so it must be disabled until generation finished. I'll disable button until ready.

Resize handling: recompute cell size on window resize, redraw.

Let me write the full file now.

Drawing function details:

```js
function draw(){
  ctx.clearRect...
  // cells background
  // fill explored etc.
  // walls
}
```

Colors:
- bg cell: #f7f4ec / white-ish
- generated-but-unvisited? During generation, cells not yet visited could be darker (unrevealed), visited lighter — shows carving progress. Nice: unvisited cells fill '#dfe3ea'? Hmm but after generation all visited. During generation, showing visited cells in white and unvisited in gray shows maze emerging. Good visual.

Actually with recursive backtracking, "visited" cells = carved region. So fill unvisited = '#e8e2d5' (fog), visited = '#ffffff'. Then walls drawn dark. That gives nice carving progress visuals.

- stack cells (current path): '#ffe0a3' or subtle.
- current head: '#f5a623'.
- explored (solver): '#cfe8ff'
- frontier? maybe '#e8f1ff' skip.
- current solver cell: '#ff9f43'
- path: '#2f6fed'
- start: '#2ea44f' with label S
- finish: '#d93025' with label F

Walls: '#2b2f38', lineWidth 2 (scaled).

Edge: drawing walls per cell with line width w; outer borders drawn correctly.

Implementation of walls drawing:

```js
const x0 = pad + c*cell, y0 = pad + r*cell;
if (cellWalls[i][0]) line(x0,y0,x0+cell,y0);
...
```
pad = wallHalf maybe. Set pad = 3 so outer walls aren't clipped (lineWidth 3 centered). I'll use ctx.translate(pad,pad).

Canvas CSS width = total. Use DPR scaling.

Let's write the code fully.

For neighbor dirs: 0 top (r-1), 1 right (c+1), 2 bottom (r+1), 3 left (c-1). opposite: 0<->2, 1<->3.

Ok now write file. Then test in browser: reload, screenshot, click New Maze during generation, check state, check console errors.

I'll write it.

Path animation: store solution array of cell indices; pathDrawProgress float 0..len. Draw line up to progress.

Solver step details:

```js
function solverStep(){
  if (bfsQueue.length===0) return true;
  const cur = bfsQueue.shift();
  if (cur===finishIdx){ buildPath; return true; }
  for each neighbor open: if !sVisited: sVisited, parent, push, mark explored.
  exploredSet.add(cur)
  return false;
}
```
Mark explored when dequeued (or enqueued). I'll mark explored at enqueue time (wavefront) — then BFS wave fills, looks nice. Current cell highlight = dequeued.

Actually if marked at enqueue, the "explored" region grows as the wave. Fine.

Edge: start===finish never here.

Also: on solver done with path found (always, since maze connected).

Let me now write the HTML.

Also add keyboard? Not needed.

Write file.

Empty dir. Write index.html.

One issue: `genStack.indexOf(i)` inside draw loops over 375 cells x stack length — O(n²) but small (375*~100 = 37k per frame) — fine, but let's use a Set or an array flag for cleanliness. Fine as is, but let's optimize: keep `onStack` Uint8Array. Let me refine for perf since draw runs every frame during generation.

Also `carved.reduce` on Uint8Array works (TypedArray has reduce). OK.

Also `sVisited[i]` when phase !== "generating" — includes "ready" moment; fine.

Let me optimize the stack lookup and then test in browser.

Wait: when genStack empties via pop in generationStep, `genDone` set on next call (genStack.length===0 check at top returns true with genDone=true). Actually the flow: after pop, returns genStack.length===0 (true) → frame breaks and checks `if (genDone)` — genDone is still false! Bug: generationStep returns true but genDone flag not set. Let me fix: set genDone when returning true at end of generation.

In frame: `for (...) { if (generationStep()) break; }` then `if (genDone)`. If generationStep returns true but genDone false, phase never transitions. Fix: in generationStep, when returning true after pop, set genDone = true. Or in frame, track return value.

Better: make frame track a `finished` boolean from the loop.

Let me restructure: 

```js
var finished = false;
for (var s = 0; s < steps; s++) { if (generationStep()) { finished = true; break; } }
if (finished) { genDone = true; ... }
```

Same for solver. Let me edit frame accordingly.

Also note the case where steps === 0 but generation already done — can't happen since once done, phase changes.

But: `if (generationStep()) break;` at start of generation where genStack has 1 element and no candidates → pops → returns true → finished. Good.

Also generationStep early `if (genDone) return true;`.

Let me apply the fix.

Also, in the "showpath" phase, `pathProgress` reveal uses `Math.floor(pathAcc)` with PATH_PX_PER_SEC_FACTOR = 26 cells/sec → path of ~50 cells takes 2s. Fine.

One more: `solution.length` might be > 1 always. If maze start==finish no.

Now run in browser.

Generation is progressing nicely — carved region visible with amber backtracking stack. Fog (uncarved) cells are visible. Good.

Now wait and screenshot later to see the solved state.

The browser tool's screenshot is a fresh snapshot; but the page continues running in the browser presumably. Let me screenshot again to see the state after 9s.

Solved state looks good: explored cells (light blue), solution path (thick blue) from S to F, unexplored cells white. Path appears to follow passages — need to verify it never crosses a wall. The path is thick (0.3 cell), so it's drawn over cells but the underlying segments connect cell centers only when passage is open. Visually it looks plausible.

Wait — hmm, the path is drawn as a thick blue line and it visually seems to "cross" wall lines? Let me check with a programmatic verification instead: run a check that the solution path's consecutive cells are connected by open walls. I can do this via the debug hook... but the debug hook doesn't expose the solution array. Let me add a validator function to the debug hook that checks:
1. All cells reachable (generation correctness) — BFS reachability count == 375.
2. Exactly one simple path: maze is a tree → number of open passages == 374 and no cycles (BFS from start reaches all with parent tree and total edges = 374).
3. Solution path consecutive cells connected.

I can compute this in the page. Let me add a `validate()` to the debug hook and run it via browser inspect/console? The browser tool has "inspect" action which reports console/DOM. Can I execute JS? Probably not arbitrary eval... Let me check if there's a way — I could use the `type`/`click` to interact. Alternative: I can write a quick node script that replicates the logic? But the wall data is generated in-page.

Better approach: add validation into the page itself and display result in the DOM (e.g., status or a hidden element), then read it via `inspect`. Or simpler: put validation results into `document.title` or a visible element. Let's add a small "self-check" line in the legend area that runs after solving: e.g. "Self-check: 375/375 cells reachable · 374 passages (tree) · path valid". That's both useful and verifiable via DOM inspection.

Let me implement `selfCheck()`:
- compute reachable count via BFS using walls.
- count open passages: sum over cells of open walls / 2.
- tree check: reachable == 375 && openPassages == 374 && no cycles (if edges == nodes-1 and connected → tree → exactly one simple path between any pair).
- path check: consecutive cells in solution have open wall between, and path endpoints are START/FINISH.

Then display. Also run the check after generation and after solve.

Also test "New Maze during animation replaces view cleanly". I'll click New Maze mid-generation and screenshot.

Let me add the self-check element and code.

Careful: `getState` calls `selfCheck()` which mutates the selfCheckEl text — acceptable (harmless, keeps it in sync). But `getState` includes `explored: exploredCount` twice now? Let me check: original had `explored: exploredCount,` before `pathLen`. My edit oldText was "pathLen: solution.length,\n        pathProgress: pathProgress,\n        walls: ..." and added "explored: exploredCount," after pathProgress. So `explored` appears twice in the object literal — duplicate key is allowed in non-strict... but the file has "use strict"! Duplicate properties in object literals are allowed in ES6+ strict mode too (only ES5 strict disallowed? Actually ES5 strict mode disallowed duplicate data properties; ES6 removed that restriction). Modern engines allow it. But it's sloppy — let me remove the duplicate.

Also selfCheck uses `scratch` array which is shared with generationStep/solverStep — fine, since selfCheck is called synchronously outside of stepping. But careful: neighborsOf(cur, scratch) in selfCheck resets scratch... fine.

Also note: `selfCheck()` called inside `getState` before `walls` field computed — fine.

Let me fix the duplicate key and then reload & test.

Wait, the original getState had `explored: exploredCount,` before pathLen? Let me check the file to make sure I didn't leave a duplicate or lose it.

Good. Now reload and test the full cycle: initial generation, then mid-generation click New Maze, then wait for solve, check self-check text.

Plan:
1. reload → screenshot early (generation in progress), click New Maze while generating → screenshot to confirm clean replacement.
2. wait ~10s → inspect DOM for self-check line.

The browser tool's `inspect` returns console+dom. Let me do reload, then immediately click New Maze at some point (need generation active — it is right after reload).

To check that New Maze during animation replaces view cleanly: click New Maze right after reload, then screenshot a moment later showing fresh carving starting from start cell again.

Sequence:
- reload
- click New Maze (x,y of button ~ (126, 92))
- screenshot immediately → should show early carving again
- sleep 10
- screenshot + inspect → self-check text.

Let me do that.

Generation active with visible carving. Now click "New Maze" mid-generation (verification requirement) and immediately screenshot to confirm clean replacement.

The view cleanly reset: previous carved region wiped back to fog and carving restarted from the Start cell (amber trail from S). Replay Solver is disabled again. 

Now wait for completion and inspect the self-check line. Also test Replay Solver afterwards (verify walls unchanged — self-check passages count same). To verify walls unchanged across replay, I'd need to compare walls before/after. The debug hook exposes walls but I can't easily eval JS... unless I can type into something. Hmm, maybe the browser tool has no eval. But I can check indirectly: the self-check line shows "passages N (tree)" — if replay changed walls, passages count would differ or it would break. Comparing numbers across screenshots works.

Sequence:
1. sleep 12 → screenshot + inspect: record self-check text (passages count, path moves).
2. click Replay Solver → screenshot immediately (exploration restarts from start) → then sleep 12 → inspect again: same passages count, path valid.

Let me do that.

Note: screenshots taken by the tool show "Frame 1, +0ms" each time — meaning the tool reloads?? Actually the DOM shown after click includes "self-check: pending…" which is written at newMaze() time, consistent. And after sleep, does the page persist? Earlier after sleep 9 the status showed "Solved", so the page persists across calls. Good.

Now inspect.

Self-check: reachable 375/375, passages 374 (tree → exactly one simple path between any pair), solution path valid (94 moves), each step through an open passage.

Note: the path line is thick (0.3 cell) and visually appears to overlap wall lines near corners? Looking at the image, e.g. right edge vertical run: it hugs the wall. The self-check proves segments connect open passages at cell-center level. Fine.

Now test Replay Solver: capture passages count before (374), click replay, verify exploration restarts and after completion the same walls (374 passages) and path valid.

Replay restarted BFS from S (orange active cell, blue explored neighbor) on the SAME wall layout (identical walls to previous screenshot) — exploration and path cleared, walls preserved. 

Now wait for completion and confirm the wall structure is unchanged (passages 374) and path valid again.

Note: is the wall layout identical to the previous screenshot? Comparing: yes, e.g. same pattern of walls. Good.

Wait ~12s and inspect.

Hmm wait — will the replayed path be the same length? The self-check line in the last inspect still showed old text ("solution path valid (94 moves)") since selfCheck only re-runs at solve completion. After replay finishes it should update with same passages 374 and same path length 94 (BFS deterministic on same maze).

Also check console for errors. Let me inspect + screenshot.

Replay produced the identical result (94 moves, 162 explored, 374 passages) on the same walls — confirming walls unchanged and BFS deterministic. No console errors (only the sandbox iframe warning from the harness).

One more quick check: mid-solver New Maze cancellation — the requirement only mentions requesting New Maze during carving, but it should also cancel a solver run. It works via the same reset path (newMaze resets solver state and phase). I could quickly verify by clicking New Maze during solving — that's a fast check. Let's do: click Replay, then quickly click New Maze, screenshot to see it generating again with no leftover blue.

Actually the sequence "Replay → immediate New Maze" would show generation fog. Let's do it quickly.

Solver is replaying (early BFS). Now click New Maze immediately to cancel it.

New Maze cleanly cancelled the running solver (no leftover blue exploration/path) and restarted carving from Start. All key behaviors verified.

Let it finish once more to confirm end state is healthy after cancellation (quick, ~12s). Then final file check.

Actually, to save time I can just confirm the file exists and is complete. But a final full-cycle check after the cancel is worthwhile and cheap. Let me sleep 12 and inspect quickly.

Hmm — the previous screenshots seem to come from a persistent browser? Note "Frame 1, +0ms" each time. Does the page keep running between calls? Earlier after sleep 9 the status was "Solved", so yes. Let me inspect.

Everything works. Fresh maze after cancel: 375/375 reachable, 374 passages (tree), path valid 84 moves. No console errors (only harness sandbox warning).

Final: confirm index.html exists in cwd.

No external references. Done. Report.