This is one of the most impressive Ti-89 games I've seen. Its actual 3D, not just ray casting. it has stairs and different heights, and the textures look pretty decent to. The gameplay is very similar to Doom.
Graphics 10/10 Best I've seen on a calculator
Gameplay 8.5/10 Gets Repetitive after a while
Speed 8/10 It takes a little to long to turn around
Replay ability 7/10
Overall 9/10 Totally Recommended
My biggest problem with this game though is there's no variety. No Key Cards To Collect, only 2 weapons, you end up just wandering through levels looking for the exit, and also there's only 5 levels. With more levels and weapons, this could be the best Ti-89 game.