Alien Spidy is a platformer in which players take control over Spidy, a spider-like creature, who crashlands on a planet in search for his friend Virgil. Spidy has to travel through 69 side-scrolling levels while jumping to avoid pits, hazardous environments (both immobile and moving) and other obstacles. He also shoots out threads which clutch to certain surfaces and are used to travel farther by swinging. Special level objects, e.g. one which allows higher jumps, and power-ups are introduced over the course of the game.
The obstacles are not meant to be overcome one by one, but the level design forces players to stay in motion and use the momentum. This is enforced by the point system which encourages speed: points are earned by collecting glowing balls which are distributed over the levels. However, their placement forces precise timing and momentum to collect. Each second removes points from the counter, so speed is of most importance in order to reach a high score. Spidy has unlimited lives and instantly respawns at the last checkpoint after dying, but every death results in a score penalty. The levels are divided into three environments with a boss fight at the end.