The aim is to guide the "seeker" through the insides of a mountain and destroy the base of an evil, tyrannical computer. Mastertronic say there are over 1000 screens to search.
Instead of a set amount of lives you are given a psyche level, the game ends when the level falls to zero. Colliding with an alien or the room surround will reduce your psyche. In some rooms there is an object which boosts your psyche level, but some give you "decayed" psyche which is fatal. You can also die by running into a proton thruster, which is a white vertical line gradually increasing and decreasing in length.
Graphics are smooth and the three different rooms are much of a muchness since there are only a few static objects present in each and the same object can be found in many rooms.
Kempston, Protek and Sinclair joystick interfaces can be used, the keys are well chosen but cannot be redefined. Instructions are reasonable though there is little relation of the plot to the game.
In most rooms it is easy to avoid the proton thruster, provided you concentrate, but the different problems give the game its appeal - these include finding bombs to blow up force fields and obtaining fuel to power a rocket to take you through a gas room.
Once you have solved a problem the game seems easy - until the next is encountered, making Nonterraqueous a compulsive game and an excellent buy.