The classic snake game played on the surface of a Klein bottle. A game made for the Arduboy.
If you have an Arduboy, check out the Arduboy Quick Start Guide to get started. With the Arduino IDE you can compile nielk.ino and upload it to your Arduboy.
Otherwise, you can use an enumulator like Sim-Arduboy to play the already compiled binary nielk.hex.
While developing this small game, I wrote two Python scripts to help me, which are both available at Arduboy-image-tools. The first, ard_img_to_bitmap.py, converts images to bitmaps (or arrays of bitmaps in the case of multiple frames). I used this to convert the background images as well as the numbers for the timer and score.
The second, ard_screenshot.py, listens to a given serial port for screenshots sent from the Arduboy. I used it to take screenshots, especially of the final frame of the game after you have lost.