Build a playable Tetris on a canvas with all seven tetrominoes, rotation, line clears, increasing speed, a next-piece preview, and score.

Build single-page web app and write it ALL into one self-contained file named index.html in current directory: CSS in <style> tag, JS in <script> tag, inline — do not create separate .css/.js files. Use NO external resources, CDNs or network requests: artifact runs fully sandboxed with no network. End with index.html present.

Current working directory: /tmp/ws

We need to write index.html file with self-contained Tetris.

No external resources. Use canvas.

Let's create file.

Requirements: seven tetrominoes, rotation, line clears, increasing speed, next-piece preview, score.

Implement basic controls: arrow keys, space rotate, down soft drop, up hard drop? Maybe.

Use canvas for board and preview.

Implement game loop with requestAnimationFrame.

Increasing speed: level up every 10 lines? Decrease drop interval.

Score.

Should be single file.

Let's write file with write tool.

Make sure CSS in style tag, JS in script tag.

No external resources.

Let's produce index.html.

We'll create nice UI.

Implementation details:

Board width 10, height 20.

Tetromino shapes defined as matrices.

Rotation: SRS? Simpler rotation with matrix rotate clockwise.

Collision detection.

Ghost piece?

Next piece preview: canvas or div.

Score display.

Pause?

We'll implement simple controls.

Use canvas for main board 300x600 maybe.

Use separate canvas for next piece.

Let's write code.

We need to ensure file present.

We'll write with write tool.

Potential improvements: hold? Not required.

Let's create index.html.

Make sure to avoid external fonts? Can use system fonts.

Ok.

Let's write.

File written. Should confirm presence.

Let's read first few lines.

Done.