Solar Fox is a space-themed variation on the once-popular "collect the dots" gameplay mechanic. Stages take place from an overhead perspective, and task you with trying to collect various arrangements of "energy cells," which are defended by roving enemy turrets. The player ship is able to fire short-range bullets, which can destroy enemy projectiles, as well as temporarily immobilize the enemy turrets.
Solar Fox contains a somewhat unique system for rewarding players who complete stages quickly. At the start of each stage, a meter with the words "skip a rack" will begin to slowly shrink. If the player manages to collect all the energy cells before this meter has disappeared, he will skip the next stage (or "rack), while still receiving all that stages' points. A button to control your ship's speed assists in this pursuit, though rushing through stages is naturally more risky than going through them slowly, adding an interesting risk-reward system to the game.
The Atari 2600 version features significant gameplay changes, and is considered (by many enthusiasts) to be superior to it's arcade counterpart, which was an exceedingly rare occurrence for 2600 ports. The number of enemy turrets was reduced, their rate and style of firing was altered, and your ship's ability to shoot back was eliminated altogether. Also, the background grid was removed, which makes the game slightly more difficult to navigate, since player movement is inherently grid-based.
The Commodore 64 version is a more faithful port of the arcade game, and doesn't contain any of the changes made in the 2600 game. It does however feature several changes of it's own.