Zombies is a platform game in which the protagonist has to fight the titular monsters, snakes, spiders, and an array of other creatures in order to survive. The game features a total of 13 dungeons with 129 different rooms. A cooperative mode with another player is also included. The game was re-released in 1984 by Electronic Arts but it was renamed to Realm of Impossibility.

The player must traverse 13 dungeons to gather seven crowns to defeat the evil cleric Wistrik. The dungeons the hero must traverse make use of visual effects, similar to those found in M. C. Escher's work, to create physically impossible scenarios. These structures serve as a basis for puzzles which must be solved in-between the fighting in order to proceed.