The object is to detonate a Photon explosive within a certain distance of a germ-laded Romulan spaceship. This ship is orbiting a planet at a constant altitude and orbital rate. The location of the ship is hidden by a device that renders the ship invisible, but after each bomb you are told how close to the enemy ship your bomb exploded. The challenge is to hit an invisible moving target with a limited number of shots.
The game is published as type-in source code in Basic Computer Games (Microcomputer Edition), ed. David H. Ahl with Steve North, Workman Publishing, New York, 1978 (ISBN 0-89480-052-3).
The BASIC source code listing is published in Microsoft BASIC 3.0; suggestions for conversion to a wide range of other BASIC implementations are provided.