<thinking> To build a playable Tetris game in a single HTML file, I need to create the HTML structure, style it with CSS, and implement the game logic with JavaScript. I will write the HTML, CSS, and JavaScript directly into the index.html file without using external files. The game will include a canvas for the Tetris board, tetromino shapes, rotation, line clearing, increasing speed, a next piece preview, and a score counter. I will use inline styles and script to keep everything self-contained.</thinking>

The self-contained Tetris game has been successfully created and written into the `index.html` file in the `/tmp/ws` directory. You can now open this HTML file in a web browser to play Tetris. Here is a brief summary of the game features included: - A Tetris board displayed on a canvas. - The game runs fully offline without any external resources. - All game logic is written inline within the HTML file. - The game includes a score counter and a next piece preview. - Basic controls for moving, rotating, and dropping the tetromino pieces are implemented. To play the game, navigate to the `/tmp/ws/index.html` file in your web browser. Have fun playing Tetris! If you need any further customization or have additional requests, feel free to let me know.