Atari 400/800/XL/XE/XEGS systems
∑ At least 2 known prototype versions exist. The earliest version isnít much more than a demo or early version of the game. A few enemies are present, but don't move or hurt you. You can run around the screen (which look slightly different), there is no POW, and you move very fast. A later version, dated 9-14-83, only differs from the released version by a few bytes.
∑ There is a slight visual difference between the 5200 version (pictures #1 and #2) and the 400/800 version (pictures #3 and #4). The small text in the 400/800 version is high-lighted.