Both the game and the source are much more minimal, it's very easy to customise the rules. You can see the source here: https://github.com/gunn/tetris/blob/master/src/store.js
pure-store is a library I made for very simple but efficient state management. The entire source is this file: https://github.com/gunn/pure-store/blob/master/src/index.ts
[1] https://github.com/yogthos/clj-tetris/blob/master/src/tetris...