Halley's Comet is speeding towards mother Earth carrying lethal bacteria cap able of wiping out all forms of life, according to the inlay. The game is obviously set in seventy six years time when Halley's Comet makes its next visit, because a highly advanced space ship has been dispatched to destroy the deadly germs that live on it. (The game turned up long after the real comet had been and gone!) The screen shows a view through the cockpit window of the shuttle with the comet shimmering in the distance and the stars scrolling towards the ship.
To begin with you assume the personality of the ship's onboard computer and have to deal with problems during the voyage the trip is far from uneventful.
Every so often one of the five icons on the main view-screen flashes to indicate that a problem has just arisen. Each icon leads into a subgame, played against the clock, in which the fault or threat has to be dealt with if the main mission is to continue. Meteor showers have a habit of knocking the antenna out of line from time to time, and it has to be adjusted until the maximum signal strength is regained.
Drifting off course sets off a defence system which releases homing missiles targetted on your ship. A Missile Command press fire when you're happy with its position type sequence then follows, and the aim is to limit the number of missiles that hit the ship, which changes colour from white through to blue before exploding when the shields give way.
Coffee supplies must be kept high vital for the pilot's reactions. A flashing coffee jug icon leads to a screenful of icons which control the whole coffee making process. By moving the cursor around and selecting icons, the coffee system has to be kept in equilibrium, including the pilot's bladder, which has to be emptied with the 't' icon lest it explode'.
Now and again, rampant germs gain access to the ventilation system of the craft and have to be eliminated in another arcade sequence in which a moving cursor is used to release spiralling germ killers. Finally, a logic problem has a habit of cropping up in a section of circuitry, and it has to be sorted out by providing the appropriate inputs to light up a set of LEDs.
The little sub games cycle round at random during the journey to the comet, and if you manage to survive them all it's time to get on with the main purpose of the mission: eradicating the germbags that live on the surface of the comet. Destroy them all, and you can return to Earth a superhero and saviour of the human race. Take too many hits from the bugs, and it's game over.