Millipede

This prototype is the version that GCC did without permission from Atari. It's not clear why GCC decided to go ahead with their own version, but they probably figured that if they upstaged the internal Atari programmers and got their version to marketing first Atari would go with it (a similar incident had happened with Battlezone). However, in this case Atari decided to stick with their own programmers and chose to release Dave Staugas' version instead.