The aliens appear as invading Spyders in Octal-1, which has optional keyboard or joystick control.

From your base in the centre of the screen, you must ward off three waves of attack for which different points are scored.

Your Octal base may be rotated through eight positions, either left or right. You fire with twin Octazer bolts. The game ends when your base is destroyed and the three highest scores shown.

In Keys Of The Castle, you have three castles to explore. Each has six floors with a maze layout and increasing hazards at each level including darkened hallways and electrified walls.

Your objective is to explore all the castles. To gain access to the next level, keys have to be collected from rooms, some of which are guarded, and taken to their correspondingly coloured chests.

All your explorations are made in a race against the clock. The game ends either when you succeed in your mission, sustain ten wounds, or run out of time. A final score is given.

J.W.