Sure! Here's a simple implementation of Tetris as a single HTML file using JavaScript and enclosed within script tags:
To play the game, you can copy this code into an HTML file and open it in a web browser (preferably on a smartphone for better experience). The game will start automatically, and you can use the left and right arrow keys to move the tetromino, the down arrow key to make it drop faster, and the Q and W keys to rotate the tetromino. The goal is to clear as many rows as possible by placing tetrominoes and achieving high scores.
Please note that this is a basic implementation of Tetris and there is scope for further improvements and enhancements.