The Ndless readme and the src/doc/Dev.txt have very useful information. Read them and if you have any other questions, feel free to ask.

If you use Linux, I can give you detailed instructions.

You probably want to code in C.

I don't have double buffering working yet, but I do have texture mapping:

The textures are only 8x8 though, since I had to hand-code them.

What is the best way to create a second buffer? I tried making a 320x240 array, but the program just crashed.

aaah ok, I was unsure. 4 levels of gray would be ok, though. Even monochrome, altough it wouldn't be pushing the Nspire to its limits as much . But we have to start small when coding anyway, IMHO. It's good to be ambitious, sometimes, but we have to make sure to not be way too ambitious either. ^^

Some people who are totally new at something will sometimes go with the largest possible RPG project, then realize it was too much for them . I usually start with something small, see if I can do it, then expand.

16-level gray is pretty easy to do, considering the Nspire has hardware grayscale support.
I don't feel this project is terribly ambitious yet. Notice I have absolutely nothing planned for gameplay--right now, I'm just experimenting with raycasting.

I think I can implement variable wall heights. The emptyness of the screen is because my walls are not very high, which is easily fixed. Right now, my biggest priority is figuring out how to get smooth motion.

From what I have right now, I think I have plenty of speed left, especially since I haven't started optimizing yet.

I finally got around to writing some code for my Nspire raycaster project. Right now it is shamefully featureless, as it basically draws untextured walls from a scene defined by a hard-coded array in the source:

The big problem I'm having right now is getting the animation not to flicker (the above screenshot was not animated). Does anyone here (maybe calc84maniac?) know how to do flickerless animation on the Nspire?
Once I get the animation working, I'll add other things, like texture mapping and sprites. Also, does anyine know how to pause execution for a specified amount of time (so I can limit the frame rate)? Right now, from my preliminary flickery code, it seems like I have plenty of speed to work with.

When they call that 'A very basic ray tracer'
Shit, soon we're gonna be able to play PSX on em

Well, it is a basic raytracer considering it only supports spheres, one light source, and a single plane.
Also, it is rather rudimentary compared to the Java program I wrote a while ago:

(The speckles are because of the way the program renders the caustics and soft shadows. The program is attached in case anyone is interested in messing with the code.)