Wow, I just googled for a youtube video of gameplay [0] and I'm genuinely at a loss at how they pulled off that 3d engine. The sound fidelity is still pretty high given the lack of dedicated sound hardware on the GBA, and somehow they still have time left over for texture-mapped polygons.

I love reading about how programmers pulled off these tricks on such limited hardware, hopefully there are some notes about it somewhere on the internet.

[0] https://www.youtube.com/watch?v=K-AZQKTlUMs