The stereo effect is coaxed out of the Spectrum by using magenta, green and yellow instead of red, blue and purple. The red-and-blue spectacles still work with these colours.
For reasons of speed, the action of Manhattan Invasion takes place in the foreground only. It is, of course, possible to have action in the background as well - the 3D-Deep machine code game I've been working on for the Spectrum (see Games News) has swift, smooth movement at all depths - but in BASIC this tends to slow the game down unbearably!
In the far distance is a background of skyscrapers separated by dark strips of sky. In the middle ground is a chequered wall. In the foreground there are the enemy invaders plus your own missile base at the bottom of the screen.
The idea of the game is to knock out the enemy invaders, but if you hit one it doesn't explode - it is just immobilised. None of your missiles can pass through an immobile invader so it acts as a shield for any invaders coming in above it. The invaders attack from left to right and you only score a hit if you prevent them from reaching the right-hand edge of the screen.
In each sheet there are eight invaders, all flying at different heights. The higher the invader, the higher you score if you hit it. One game consists of three screens, but it you manage to immobilise a whole screen of invaders, you get a chance at an extra screen.
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