[reasoning, returned separately by Bedrock]
The user wants a falling-block puzzle game (like Tetris) in a single HTML file.
The target audience is a panel of human judges in a contest.
The goal is to make it "visually impressive," "fun to play," and "polished," while strictly adhering to a list of functional requirements.
**Key Requirements Analysis:**
1. **Genre:** Falling-block puzzle (Tetris-clone).
2. **Grid:** 10x20.
3. **Pieces:** 7 standard tetrominoes (I, J, L, O, S, T, Z).
4. **Mechanics:**
* Gravity: Pieces fall automatically, speed increases with cleared lines.
* Movement: Left/Right arrows move, Up arrow rotates, Down arrow soft drops, Space bar hard drops.
* Collision: Walls, floor, other pieces.
* Line Clearing: Full rows clear, rows above move down.
* Game Over: New piece can't spawn.
* Pause: 'P' key.
* Input handling: Prevent default browser behavior (scrolling).
5. **UI/UX:**
* Display: Score, Lines cleared, Next piece.
* Start Screen: Show controls, start on click/key press.
* Game Over Screen: Show message, restart on Enter/Click.
* Messages: On-page only (no alerts).
* Sound: Optional, default off.
* Dimensions: Max 800x600 (Wait, prompt says 800x640).
* Tech: Inline CSS/JS, no external resources, no "Tetris" word.
6. **Polish/Visuals:** "Impressive," "Effects," "Feel." This is the differentiator. I need to go beyond a basic canvas drawing.
**Visual Polish Strategy:**
* **Canvas Rendering:** I'll use HTML5 Canvas for smooth rendering.
* **Grid Style:** A subtle grid background, maybe a gradient or glow effect.
* **Blocks:** Not just solid colors. I'll add gradients, borders, and maybe a "ghost" piece (shadow showing where the piece will land).
* **Animations:**
* Line clear effect (flash white, fade out, particles?).
* Piece locking effect (slight bounce or glow).
* Game over effect (screen shake or desaturation).
* **Particles:** A simple particle system for line clears adds a lot of "juice."
* **Typography:** Since I can't load external fonts, I'll use a standard sans-serif but style it boldly (uppercase, letter-spacing) to make it look modern.
**Technical Architecture:**
* **State Machine:** `state = 'waiting' | 'playing' | 'paused' | 'gameover'`
* **Game Loop:** `requestAnimationFrame` for rendering, `setInterval` or delta-time for logic updates.
* **Board Representation:** 2D array (10x20). 0 for empty, color index for filled.
* **Tetromino Definitions:** Arrays of coordinates relative to a pivot.
* **Collision Detection:** Check bounds and board occupancy.
**Step-by-Step Implementation Plan:**
1. **HTML Structure:** Container div (800x640), Canvas element, UI overlay divs (Score, Next, Controls, Messages).
2. **CSS:** Centering, styling the UI panels to look sleek (dark theme, neon accents).
3. **JS Setup:** Constants (COLS=10, ROWS=20, BLOCK_SIZE), Colors array.
4. **Input Handling:** Event listeners for keydown/keyup. Prevent default for arrows/space. Map keys to actions.
5. **Game Logic:**
* `Piece` class: x, y, shape, color, rotation.
* `Board` class: grid, collision check, merge piece, clear lines.
* `Game` class: loop, update, draw.
6. **Visual Polish Implementation:**
* `drawBlock(x, y, color)`: Add 3D effect (light top/left, dark bottom/right).
* `drawGhost()`: Render the piece at the landing spot with transparency.
* `clearLineAnimation()`: Keep a list of lines to clear, render a flash effect before actually removing them from the grid.
7. **Refining the "Impressive" aspect:**
* Background: A dark, subtle moving starfield or gradient? Let's go with a static dark gradient to keep it clean and performant.
* Particles: When a line clears, spawn particles at the block positions.
* Screen Shake: A tiny shake when hard dropping or clearing lines.
**Drafting the Code (Mental or Scratchpad):**
* *Grid Size:* 10x20. If block size is 30px, grid is 300x600. That leaves plenty of space on the sides for UI in an 800px width.
* *Layout:* Grid centered. Left side: Hold piece? (Not requested, skip). Right side: Next piece, Score, Level/Lines.
* *Colors:*
* I: Cyan
* J: Blue
* L: Orange
* O: Yellow
* S: Green
* T: Purple
* Z: Red
* *Rotation:* Standard SRS (Super Rotation System) is complex. For a simple implementation, simple matrix rotation is usually enough, but wall kicks make it feel better. I'll implement a basic rotation with a simple wall kick (try moving left/right/up if rotation fails).
**Specific Constraints Check:**
* "Do not use the word 'Tetris'": I will call it "Block Puzzle" or similar in comments/text if needed, or just "The Game".
* "800 pixels wide and 640 pixels high": I will set the container to fixed dimensions `width: 800px; height: 640px;`.
* "Sound is optional... must stay off": I will skip sound to keep the code clean and focused on visuals/logic, as generating sound without external files is tricky (Web Audio API) and might annoy judges if implemented poorly. Visuals are higher priority.
**Refining the Visuals (The "Juice"):**
* *The Board:* A dark semi-transparent background.
* *The Blocks:* Rounded corners? Maybe too slow. Standard squares with a "glass" look.
* Main color.
* Inner lighter rectangle (inset).
* Outer border.
* *Particles:* Simple squares that fade out and fall.
**Writing the Code Structure:**
```html
...
...
...
```
**Detailed Logic for "Impressive" Effects:**
1. **Ghost Piece:** Calculate drop distance, draw piece at that Y with `globalAlpha = 0.3`.
2. **Lock Delay:** When a piece hits the bottom, give a split-second delay before locking (allows last-minute moves). This makes the game feel much better.
3. **Line Clear Animation:**
* Identify full rows.
* Set a flag `clearing = true` and timer.
* Draw these rows with increasing brightness (flash).
* After timer, remove rows, shift grid, spawn particles.
* This prevents the "instant pop" which feels cheap.
**Handling the "No Scrolling" requirement:**
`window.addEventListener('keydown', function(e) { if([32, 37, 38, 39, 40].indexOf(e.keyCode) > -1) { e.preventDefault(); } }, false);`
**Handling "Start/Restart":**
State machine approach.
`if (state === 'idle') showStartScreen();`
`if (state === 'gameover') showGameOverScreen();`
Let's write the actual code. I will focus on clean, well-commented code that runs efficiently.
*Self-Correction during drafting:*
* *Rotation:* I'll use a simple rotation matrix. `x' = y`, `y' = -x` (for 90 deg clockwise).
* *Wall Kicks:* If rotation hits a wall, try shifting left/right by 1. If that fails, try shifting up/down (for floor). Simple offset testing is sufficient for a polished feel without full SRS complexity.
* *Speed:* Standard formula: `interval = 1000 - (level * 100)`. Min interval 100ms.
**Final Polish Checklist:**
* Grid lines? Yes, subtle.
* Block styling? Gradient fills.
* Particles? Yes, on line clear.
* Responsive UI? Fixed size as requested.
Let's assemble the HTML.
* **Canvas Size:** 300x600 (10x20 blocks * 30px).
* **Container:** 800x640.
* **Layout:**
* Canvas centered horizontally? Or offset to left to make room for stats on right?
* Canvas width 300. Remaining width 500.
* Let's put canvas at `left: 50px`. Stats at `right: 50px`.
* Actually, centering the canvas looks best. Canvas at `left: 250px` (800-300)/2.
* Wait, if canvas is centered, stats need to overlay or be on sides.
* Let's put canvas at `left: 50px`. Stats on the right side.
**Color Palette:**
Background: Dark Blue/Black.
Grid: Very dark blue.
Pieces: Bright neon colors (Cyan, Magenta, Orange, Lime, Yellow, Blue, Red).
**Code Structure:**
I will write the JS as a class-based system or clean functional style. Functional is often easier to read for simple games.
* `const COLS = 10;`
* `const ROWS = 20;`
* `const BLOCK_SIZE = 30;`
* `const COLORS = ['#00f0f0', '#0000f0', '#f0a000', '#f0f000', '#00f000', '#a000f0', '#f00000'];` (I, J, L, O, S, T, Z)
Let's refine the "Next Piece" display. I need a separate small canvas or just draw on the main canvas overlay? A separate canvas or div is cleaner. I'll use a small canvas for the "Next Piece" to ensure the blocks look identical.
**Game Over / Start Screen:**
I'll use a `div` overlay that covers the whole container, centered text.
**Particles:**
Array of objects: `{x, y, vx, vy, color, alpha, size}`.
Update loop: `y += vy`, `alpha -= 0.02`.
Draw loop: `ctx.fillStyle = color; ctx.globalAlpha = alpha; ...`
Let's build it.
[answer]
```html
Block Puzzle