Sure! Here's an example of a simplified version of "Terraria but Tetris" game implemented as a single HTML file using JavaScript:
This simple implementation provides a game board, where tetromino blocks of different colors fall down. When a row is complete, it is cleared, allowing the blocks above to move down. The game keeps running until the player finishes playing.
Please note that this is a basic version, and you can expand it further based on your requirements and preferences.