https://ofrak.com/tetris/

This game is Tetris, but the blocks are assembly instructions that
run on a full, in-browser CPU emulator.

This game requires WebAssembly to run.

The game includes a WebAssembly-based emulator to execute CPU
instructions. Please enable WebAssembly, or use a browser that
supports it to play.

This game requires Javascript and WebAssembly to run.

It runs a Javascript-based CPU emulator entirely in the browser, and
only has a static back end to serve it. Hence all gameplay logic
takes place in the front end.