I first got really interested in programming freshman year of high school, when I got a TI-89. I loved to program on it, but the standard way to program (TI BASIC) had severe limitations (though it was still more powerful than the TI-85 I messed around with in middle school). This led me to learn C, using TIGCC, which allows you to compile C code and execute it on a TI-89 (or a TI-92+ or a V200). I made a handful of games, including a falldown clone, a simple car driving game, a shoot-em-up game with rich graphics called Super Alien Strike, and a tank game called Tankers.
My first C game.
Tankers was by far my most successful game. The terrain graphics were taken from a gameboy game, but I did all of the programming. The best feature, which isn’t shown in the screenshot, is the ability to connect two TI-89s together and play multi-player. I have always loved the idea of multi-player games. I also created a PC based map editor for creating Tankers maps (I also love the idea of user-contributed content). There is an entire directory dedicated to maps for Tankers on the most popular TI calculator archive website, ticalc.org.