Let me build a comprehensive Wolfenstein 3D-style raycasting maze shooter. This needs to include:

1. **Raycasting engine** - Cast rays from player's viewpoint to render walls
2. **Maze generation** - Procedural maze
3. **Procedural textures** - Brick, stone, etc. generated via canvas
4. **Player movement** - WASD for movement, arrows/mouse for turning
5. **Enemies** - sprites in the maze that can be shot
6. **Shooting mechanics** - Crosshair, shooting enemies
7. **UI** - Health, ammo, minimap

Let me think through the architecture:

- Map: 2D grid, procedural maze using a simple algorithm (random DFS or similar)
- Textures: Generate brick/stone textures programmatically on offscreen canvases
- Rendering: DDA raycasting algorithm for walls, with texture mapping
- Floor/ceiling rendering: Optional but nice - solid colors or simple gradients
- Enemies: Billboard sprites rendered after walls, with simple AI (chase player)
- Shooting: Raycast from center of screen, check if it hits an enemy
- Sound: Could add simple Web Audio API sounds for shooting

Let me write this as a single HTML file with everything inline.

Key technical details:
- Canvas rendering at ~320x200 scaled up (or full res with subsampling)
- DDA algorithm for wall hits
- Z-buffer for sprite clipping
- Enemy AI: simple pathfinding toward player
- Multiple texture types for variety

Let me code this up properly. I'll go with a fixed internal resolution and scale it up for performance.

Actually, let me think about the maze generation. I'll use a recursive backtracker for nice mazes.

For textures, I'll generate:
1. Red brick wall
2. Stone wall  
3. Blue/grey metal wall
4. Door texture

For floor/ceiling, I can do simple floor casting or just solid colors with shading.

Let me write the full implementation now.

Let me verify the file exists and looks correct.

The file looks good. Let me review the code once more to make sure there aren't any bugs. Let me check a few things:

1. The sprite rendering - the camera transform might have issues. Let me re-check the raycasting camera space transform.

Actually, looking at the sprite rendering code, I'm doing:
```
const transformX = (dx * cosA + dy * sinA); // depth (forward)
const transformY = (-dx * sinA + dy * cosA); // lateral
```

This is the standard LWC (Lode's Wolfenstein Camera) transform. The screen X should be:
```
const screenX = ((SW / 2) * (1 + transformY / transformX / Math.tan(HALF_FOV))) | 0;
```

Wait, that's not quite right. The standard formula uses:
```
screenX = (SW/2) * (1 + transformY / transformX * (1/tan(HALF_FOV)))
```

Actually `transformY / transformX` gives the tangent of the angle from center, and we need to relate that to FOV. Since FOV/2 maps to screen half-width:
```
screenX = (SW/2) * (1 + (transformY/transformX) / tan(HALF_FOV))
```

That's what I have, which should be correct.

Let me also think about potential issues:
- The exit tile (value 2) - collision detection needs to allow walking on it. In the update function, I check `=== 0 || === 2` for movement. But in `castRayFrom` I check `> 0`, which would include exit. That means you can't see through exit tiles. Let me check... actually exit is placed as `map[exitY][exitX] = 2`, and in DDA, walls with value > 0 are solid. If a ray hits it, it's a wall. But it should still be rendered (as a door texture). The player walks TO it but the value 2 is both passable and renderable. Wait, that's a contradiction - the collision code lets you pass it, but the DDA treats it as a wall hit.

Hmm, this is a problem. The DDA treats map[y][x] > 0 as a wall hit, but I want the exit to be walkable. Actually, let me reconsider. The exit check is:
```
if ((player.x | 0) === exitX && (player.y | 0) === exitY)
```

So the player stands ON the exit tile. But since the raycaster treats it as a wall, rays will stop there. That's... actually kind of fine visually - it'll look like a door the player is approaching. But since the player walks INTO it, it gets weird.

Actually the collision code checks:
```
if (map[player.y | 0][(newX + margin * Math.sign(moveX)) | 0] === 0 ||
    map[player.y | 0][(newX + margin * Math.sign(moveX)) | 0] === 2)
    player.x = newX;
```

So the player CAN enter the exit tile. Once they're inside, rays looking at that tile from inside would try to start at mapY = exitY, which is the current position. The DDA starts from the player's position, so the first tile it checks is the next one. That should be fine.

But wait - if the player is standing ON the exit, and they look at it from a distance away, it'll render. If they're on it, they won't see it as a wall because rays originate from their position. This is fine.

Actually, the issue is that when the player approaches the exit from a hallway, they'll see it as a wall (green door). When they get close enough to step on it, the collision allows them to pass through. But they're supposed to STOP at the exit. The code says:

```
if ((player.x | 0) === exitX && (player.y | 0) === exitY) {
    const alive = enemies.filter(e => !e.dead).length;
    if (alive === 0) {
      nextLevel();
    }
  }
```

So when they step on it and enemies are dead, level advances. If enemies aren't dead, it shows a message. This should work fine.

One issue: in the collision section, the player can walk onto exit tiles (value 2), but when checking walls that should block them, it allows exit tiles. But the exit tile IS blocking for rays, which means from the player's perspective it looks like a door they can't pass. But they CAN pass through it. This might feel weird - let me fix it by making exit tiles not block at all (just render differently).

Actually no, it's fine. The exit tile IS a rendered wall until you're on top of it. It gives the visual impression of a door/exit. Once you're standing on it, you don't see it anymore (you're looking past/through it). This is actually the right behavior - it looks like a door and you know it's the exit.

Let me also check the collision more carefully. The collision check:
```
if (map[player.y | 0][(newX + margin * Math.sign(moveX)) | 0] === 0 ||
    map[player.y | 0][(newX + margin * Math.sign(moveX)) | 0] === 2)
```

This only checks one dimension at a time, so it allows sliding along walls. Good.

I think the game should work. Let me make sure there are no JS errors by checking the code structure once more...

Actually, I notice the `spawnEnemies` function is called correctly, and the game loop starts on click. Let me also check if there's a potential issue with the exit placement - the `placeExit` function marks `map[exitY][exitX] = 2`, but the maze generator might not have opened that cell. Let me check...

The maze carves paths at odd coordinates (starting from 1,1, moving by 2). The exit is placed at:
```
exitX = MAP_W - 2 - (Math.random() * 3 | 0); // 17-19
exitY = MAP_H - 2 - (Math.random() * 3 | 0); // 17-19
```

With MAP_W = MAP_H = 21:
- 21 - 2 - 0 = 19
- 21 - 2 - 1 = 18
- 21 - 2 - 2 = 17

These are odd numbers (17, 19) or even (18). The maze carves at odd coords (1, 3, 5, ...). So exit at 17 or 19 would be at carveable positions (odd). But 18 is even and might be a wall. The `placeExit` function has a retry loop of 100, so it'll eventually find one. But wait, it just picks from 17-19 and retries if `map[exitY][exitX] !== 0`. If the cell is a wall (1), it might retry and find another. If it picks 17 or 19 (odd coords), they should be open since the maze carves through them.

Actually, even coordinates in the maze might be walls or open passages depending on the extra openings. The maze carves at (1,1), (1,3) etc., and connects them by opening the cell between them. So cells at even coordinates between two odd cells might be open (connecting passages). The `placeExit` retry should find an open cell within 100 attempts.

But there's another issue - after setting `map[exitY][exitX] = 2`, the next line is:
```
map[exitY][exitX-1] = map[exitY][exitX-1] || map[exitY][exitX-1] === 0 ? 0 : 0;
```

This line is a no-op! It always evaluates to 0 regardless. Let me trace through:
- If `map[exitY][exitX-1]` is truthy (1 or 2): `truthy || ... ? 0 : 0` → 0
- If `map[exitY][exitX-1]` is falsy (0): `0 || (0 === 0)` → `true ? 0 : 0` → 0

So it always sets the cell to 0, which is actually fine - it clears a path toward the exit. Not elegant but functional. Actually wait, that's the intent right? To ensure at least one neighbor is open? Let me re-read... yes it ensures the cell to the left of exit is open (0). This guarantees access.

OK, the code should work. Let me also think about whether the sprites need the correct distance. In the sorting, I use `dist: dx*dx + dy*dy` which is squared distance. That's fine for sorting purposes. The actual depth in camera space is `transformX`.

I think the game is functional. Let me test it mentally:
1. User clicks → starts game, generates maze, spawns enemies, places exit
2. WASD moves, mouse turns, click shoots
3. Raycasts render walls with textures
4. Enemies are visible as sprites, can be shot
5. Kill all enemies → reach exit → next level
6. 5 levels, then win screen

I think this should work well. Let me just double-check one more potential issue: the `castRayFrom` function used for enemy AI line-of-sight. It starts from enemy position and checks if it can reach the player. If it does, enemy becomes active. This looks correct.

One concern: when the player is right next to an enemy and shoots, does the hit detection work? Let me check:
```
const wallDist = castSingleRay(rayAngle);
if (dist > wallDist) continue;
```

The enemy is very close, so its distance should be less than the wall distance. The perpendicular distance check:
```
const perpDist = Math.sqrt(perpX * perpX + perpY * perpY);
if (perpDist < enemyWidth && dist < closestDist)
```

With enemyWidth = 0.35 and the player looking directly at the enemy, this should work.

I'm satisfied the game should be functional. Let me provide the response.