If you play Doom on your calculator, you'll no longer be stuck with greyscale gibs. A new update to the TI-Nspire port of the game has added support for color screens, along with some control and menu tweaks. If the demonstration below is any indication, it runs only a bit less smoothly on a TI-Nspire CX than it does on a smartphone, and can use either the d-pad or keyboard. It's supposed to work on any TI-Nspire model, not just those with touchpads.
The port, called nDoom, works with the new version of the Ndless unlocking program, which can be found here. Sound is probably the last major thing missing from this port — it's possible to play sound from a calculator, but the music in the video below is from an outside source. This software is untested by us, so the normal warnings apply... at least hold off until after your calculus finals.