Cobalt is a program for painting textural and expressive pixel-art on Windows, Linux, Nintendo DS, and in-browser. The same 46KB core executable runs on all platforms, with a thin emulator layer sitting on top to handle differences in inputs and filesystem access (which makes it easy to port between systems). It's built on Bedrock[0], an 8-bit virtual computer system I posted about here in July.
I created Cobalt because I wanted to draw messy, gritty pixel art without smooth gradients, and the smaller colour palette helped with making bolder colour choices. Images can be moved back and forth between platforms, so you can copy works-in-progress to the DS to keep working away on the bus or train. It's like a 2004-era vision of the future.
There's a live demo on the linked page that runs in the browser, and there are downloadable demos for every platform here[1]. Let me know if you try it out or have any questions!