What is this?

This is a game similar to 'Puyo Puyo' written in Javascript that runs in a browser.

What is puyo puyo?

https://en.wikipedia.org/wiki/Puyo_Puyo

About code

This code was salvaged from old PC.
This code is quite old and difficult to read.

How to play

Key bindings
[arrow left] - move left
[arrow right] - move right
[arrow down] - rotate right
[F5] - restart

Code Golf

Tried code golf on this code.
https://github.com/y-hatano-github/js-puyo-cg