GBA Games
I started programming GBA games from before launch using some early dev kits that we received at THQ. Its a really great platform to develop for. Although the total resources you have are modest ( a 16 bit cpu, with 256k of main memory ), the machine itself is designed well and is very well balanced. It is a real pleasure to try to get the most out of it. GBA uses an ARM processor, which has the best opcodes I have ever worked with. It has a very well designed 2d graphics chip. You can tell when you are working with it that the designers of the 2d chip had a lot of experience making 2d games. Everything you need is available and easy to use.
In the last three years, between 2000 and 2003, I have contributed to 9 shipping GBA games. I wrote a large amount of the game engine code used in all these games. I was also lead programmer on 4 of the 9 games, Rocket Power: Beach Bandits, Star Wars: New Droid Army, Jimmy Neutron: Jet Fusion and Rayman: Hoodlum's Revenge.
The game engine architecture that I put together at Helixe for the first game has worked out really well. We able to reuse large amounts of the game code that we wrote even in our earliest games in all the subsequent Helixe games. The game engine has been continuously updated, and some if it is now being used on some new Helixe games for Nintendo DS.
I developed the Rayman game as part of my new game development startup, Oroboro Interactive, using a whole new game engine. Its an even
better engine than what we did at Helixe. Unfortunately I don't know how much use this new game engine will get because I may move on
to a new platform this year.