Battlezone was originally an Atari arcade game.
You are in charge of a tank and your mission is to destroy the enemy tanks.
Like the original, the graphics on the Spectrum version are made up of straight lines which are used to draw all the banks and missiles.
Some clever programming means that the objects come towards you in 3D, with the computer performing what's known as hidden line removal. This means making sure that, if one side of a tank is obscured by something, the invisible part is not drawn on screen.
With Quicksilva's game, the graphics are all drawn in green on a black screen with the background the same colour. At the top, the score panel is in purple but still on black.
Realtime's version is called 3D Tank Duel and has different background colours for the land and the sky.
The 3D movement is the key to a good version of Battlezone and I found Realtime's the smoother. Both games have blocks which you can use as shields and moving in and out of them produced some good effects.
Realtime's also has some special features. Pressing the 4 key will copy the screen to a printer which will give you a print of the high score table if you want one.
Control for both games is via keyboard or joysticks. You look at the radar at the top of the screen and manoeuvre your tank accordingly. There are four keys used to move the tank - two for each track. Each can be moved forwards or backwards so to turn round at double speed you move one track in each direction.
So which one to buy? Frankly, I think that Realtime's 3D Tank Duel just comes out on top and, at £1.45 less than the official Quicksilva offering, it's also better value.