This is the official version of Sega's classic 3D arcade game, manufactured in the states by Datasoft and imported into Britain by Centresoft in their US Gold series.

It's a very faithful conversion that plays with great smoothness and has, even in the 16K version under review here, nearly all the features that you battled through in the arcades.

You control an extremely manoeuvrable aircraft and must penetrate two space fortresses and two expanses of outer space before getting the chance to destroy the Zaxxon robot.

These fortresses are peculiar and dangerous places with weaponry that is a mixture of the futuristic and the remains of a World War Two destroyer.

You begin in space. A meter at the side of the screen shows your altitude. Suddenly you encounter a wall, the first of many. You climb and then swoop down to destroy the gun emplacements. To maintain fuel levels destroy the red fuel tanks.

So you weave from side to side, climb and dive - all the time blasting away and dodging enemy fire. Eventually you reach the end of this blue corridor.

One last wall to climb over and you're in outer space. Here, blue enemy fighters zoom out of the darkness. Destroy as many as you can.

Now you reach the second fortress. It's similar to the first, but much more difficult because all the walls now have a force field at the top - there's only the narrowest of gaps to squeeze through. This takes a lot of practice. If you succeed, you will encounter the Zaxxon Robot whose destruction is your ultimate goal. Kill it and you can go through the whole business again - at a higher level of difficulty.

Zaxxon is a very classy shoot'-em-up. It provides a real challenge, is beautifully smooth to play and should keep you busy for hours