IMHO, that game sold a lot of Atari computers. Was written by the guy who designed the sound chip, and it was kind of a side project that turned out great enough to showcase the computers.
The particle calculations are not well optimized. While this is seen as a bug, and there is an effort to make the game run faster, many players appreciate the slowdown in battle. There is a feel associated with that which adds a lot to the overall impression of the game. It's oddly gratifying to feel it slow down as the enemy and their shots explode...