Exterminator is a game in which you are chased by robots. The robots are relentless but stupid. Your job is to escape the robots by destroying them.
The game is played on a grid. Each turn, you may move one square in any direction (including diagonally) or stay put. After you make your move, the robots will all move. The robots will always move directly toward you. If two (or more) robots to crash into each other, they will be destroyed and leave a heap of toxic wreckage behind. If a robot runs into a toxic heap, it will be destroyed also. If you run into a robot or a toxic heap, or if a robot catches you, you're dead.
Since the robots always move directly toward you and are oblivious to any other part of their surroundings, you can try to lure the robots into each other or into the toxic wreckage, thereby destroying them. You earn a point for each robot you destroy; when all the robots on a level are destroyed, you advance to the next level where there will be more robots.
There are two additional moves you can make besides moving from one square to another. Once per level, you can "zap" any and all robots in any of the eight squares adjacent to you, destroying them. You may also choose to "teleport" to a random new location on the playfield. (Note, however, that there is a very small chance that the new location you teleport to will be the same place you teleport from.) The availability of the "teleport" option depends upon the mode of play.
Source: The Game Website.