VVVVVV is a cute little indie game that a lot of people probably played about 10 years ago.
https://store.steampowered.com/app/70300/VVVVVV/
It's pretty "interesting" code:
This engine is super fussy about optimization levels and runtime checks.
There are lots of things about this old code that could be cleaned up, polished, rewritten, and so on, but this is the one that will probably bite you the hardest when setting up your own build, regardless of platform.
After changing a lot of code from #ifdef linux to #else (only really windows needs special treatment in most cases), it builds and appears to work on NetBSD. You still need a copy of the original data files:
games/vvvvvv
