I wrote this in order to improve my Emacs Lisp skills and to use practically by teaching my sister to program. It is the first elisp program of any substantial complexity I have written, so feedback is appreciated.
If you're wondering, Chip-8 did turn out to be a good fit for a beginner. It has limited amount of instructions and is quite graphics-oriented. Having everything inside of Emacs was also quite convenient.
Good work! This kind of thing really showcases Emacs as an application platform, able to do a lot with very little code.