Missile Defence is a conventional Space Invaders-type game in which you attempt to shoot down marauding aircraft, their smart bombs and showers of missiles before all your assets are wiped out by them.
All are accurately targeted on your installations, and to attack them you move a sight around the screen with the cursor keys.
Pressing the fire key then launches a missile from one of the three silos, and a convincing nuclear cloud appears in the target area, destroying anything nearby, and earning you some points for whatever you hit.
Very satisfying, but the enemy is still coming. If you survive, you start another round with fresh missiles and a higher level of difficulty.
The game can be played from the keyboard or a Kempston joystick. It loads easily and then offers a colourful but silent demonstration and a set of instructions to supplement those on the insert.
These repeat until you stop them to go into the main game, which has good sound effects and displays the present score and best score so far.