As you might guess from our hero's name, your aim is to save something - no less than strands of DNA, crucial to the continuation of your race. In the cassette wallet there's a half-page story which outlines the scenario. You control Xavior, who is pretty large but quite well animated, even if he does waddle up the screen. Control is key-definable or joystick.

The display is the standard square with action to the left, gauges down the right. Instrumentation includes counters for DNAs Linked, Bugs Purged, Orbs Unused and an Orb Meter.

The action takes place in rooms linked by hexagon-shaped blue doors. Some rooms contain orbs, which must be collected to keep up strength, needed to get through the doors. Others contain fragments of the DNA which have to be collected. Unfortunately, the rooms are monitored by a security system which is activated as soon as you enter, and a host of nasties slowly materialises.

You can dodge them if you're nimble-fingered, and you can hurl orbs at them. This may help your rating when you've lost your third life, but don't be reckless, as you only start with 2,048 of them. Unfortunately, the orbs don't bounce around.

There are supposed to be 4,096 rooms, and 32 designs. Many of the locations look rather similar but the monsters are varied and neatly animated.

Xavior is so complex and difficult that it should keep you amused for hours.