vdub_bobby has released a new version of his game M4 for the Atari 2600. This is probably the last version (tho he said that few times already). Changes:

Most notably: the tanks move at half their former speed. This matches up better with the arcade original.

Second-most notably: big modification to AI.

Added color mode back in, is now the default. Switch between color and B&W with, counterintuitively, the COLOR/B-W switch Slight tweaks to graphics; mostly the explosion graphics.

Slight tweaks to sound.

http://www.atariage.com/forums/index.php?showtopic=67921&st=25