If one takes the "19yo" claim at face value, this is a prodigious feat.
Obscene stuff like this seems perfect for the young. Not quite at the same level, but I wrote a custom tiling GUI in befunge when I was 19 (well, the befunge program output draw instructions which were rendered by a traditional C program). Now, 19 years of professional software engineering later, I don't think my actual code-outputting skills are much better than they were at 19 - all I have now is more knowledge abo…
Yeah, I can kind of relate, actually! Now I am 19, have a job and attend a somewhat demanding university, outside of (more useful?) real world research I am currently doing. I wrote the code when i was c.a. 15 - 16, I could definitely improve upon my Lisp - it's within my range of current capabilities, but I would not have the motivation to :-).