Illusions is a surreal, puzzle-like maze game in which you help little blobs called Gleebs escape a Mirror Dimension. The Gleebs travel in predetermined pathways along stairways, ramps and flat surfaces atop a castle-like structure. They all move at the same speed and in the same direction. You can't control them individually, but you can make all of them jump (at certain jump points along the maze) or change direction simultaneously.
To rid the Mirror Dimension of Gleebs, you must guide their movements in such a manner as to have them collide into each other. When one blob touches another, two become one. When you have reduced the entire Gleeb population to one, it will leave through a looking glass.
To make your mission more difficult, lizards appear onscreen to add more Gleebs. You can use beakers of liquid to vanquish the lizards, effectively turning them to fish. If you can guide a Gleeb to touch a fish, you will get extra time. Also, Birds will make an occasional fly-by; touch one of these and you'll lose time.
After you escape the Mirror Dimension, your journey is not over. You'll enter a strange cubic land where the objective is reversed -- you must keep the Gleebs apart. Separation points are located in the corners of the cubes. You can't jump in this level, and lizards can only bite when standing on a corner of a cube. There are no beakers of water, but lizards can spontaneously turn into a fish and then metamorphoses into a bird.
Illusions ends only when five minutes have elapsed during a level and you have yet to complete your objective.