That collection is technically kind of interesting too. The puzzle code itself is written in portable C, using a custom-built common framework and UI abstraction layer that allows it to run on pretty much any platform.
Want to write an application that does X? Design, build, test, and document a flexible cross-platform framework that can safely and portably run any application in the domain, and then specialize it to do X!
I have to say, though, that it seems to have actually worked out for the best in this case. He added a ton of puzzles at a rapid pace and they've spread to a surprising number of platforms.