Below are stills from video captures that I recently made (thanks to Bitshifter for loaning me the TV adapter) showing some alpha stage visual applications that I wrote for the GameBoy Advance.
With the exception of one that uses sprites, the rest are similar to my GP2X applications. Basically a bunch of equations that can be chosen with a button and variables that are mapped to the D-Pad, so as the player pushes up/down right/left the visuals change.
The GBA uses a 16.78 MHz ARM processor and at that speed it's kind of crazy to be writing individual pixels to the screen, but something that I wanted to try after doing it with success on the GP2X.
There's also a video available on my You Tube Channel.