That's just the colorization. Here's actual elisp by Steve Sprang (ssprang):

https://github.com/sprang/emacs-2048

Correction: Steve's above code is another implementation.

Colorization is against Zachary Kanfer's (zck) implementation in MELPA, which is here:

https://bitbucket.org/zck/2048.el

And don't miss David Thompson's (davexunit) Guile version mentioned below.

I'd much prefer to see these core code packages in the spotlight over the OP's mere colorization link.