Imagine a Mechanical World. An enormous chain of cylinders, each rotating to produce the required centripedal force which acts like gravity against the inside. Viewed from a distance, the world appears like a giant caterpillar moving through space. From a little closer the fine detail on the inner surface of each fantastic cylinder becomes clearer. The cities, fields, factories, power stations and military bases of a highly advanced alien race become apparant. Their world is perfect. All natural disadvantages such as disease or adverse climate were eliminated in the design stage. The inhabitants are imaginative, innovative, but also warlike. The conquest of other lesser worlds is their religion. Their course is set for Earth. Several missions from Earth have failed to deter the invaders. You, the player, have been despatched in the latest military spaceship to try and infiltrate and destroy the enemy from within. Each of the cylinders has a specific purpose. Some are residential, some military, for example. In addition to this, combat defence DROIDANS patrol the cylinders. Some DROIDANS are more deadly than others. Each cylinder is in contact with its neighbouring cylinder. Actions at an early stage can make later levels easier - or downright murderous!