Well Ludum Dare is underway, here is my game so far. Its meant to be satire. You play games on your calculator, and when you beet a game, your caluclator gets upgraded and you get to play a better game.
Requires java and a modern GPU, but it should run on all OSs.
https://drive.google.com/file/d/0B4B_lqaVH02oMlQ3cnJEU0RRZFk/view?usp=sharing
Do you have screenshots or a video? I cannot run it it seems (Java exception error on startup)
Glad you are participating, by the way :)
EDIT: Nevermind I got it to work now. But I think you should use a TI-82 Advanced, because it would fit your description more. The TI-81 doesn't even have a getKey command, let alone an Output() one, so it might be better if you used the TI-82 Advanced or TI-84 Plus-T. :P
So you can only get up to the 84+? You should add the CSE and the CE, and Nspire.
And I guess you need to allow progressing, I beat the pong game, got a score of 26, and it froze on highscore. :P