Sub puts you in command of an American frigate, roaming the high seas on a mission to hunt down those bad, bad Russians in their submarine and sink them.

Protek's Hunter Killer has already set the standard in this class of game for the Spectrum, and by comparison Romik's game seems very rudimentary. It will, however, fit into 16K.

The instrument panel gives information on your heading and speed, and tells you the enemy sub's approximate position and depth.

Game controls are simple. You can steer port or starboard by adjusting the rudder angle. Apart from your speed. the only other variable over which you have control is the depth at which your anti-submarine charges are set to explode.

The information is all rather crudely presented. A large circle in the centre of the screen gives a visual trace of your direction and speed, and a small square in the corner does the same for the enemy. The function of these two 'radar screens' is not fully documented.

When you actually get down to playing the game, you find it very difficult indeed. Basically you want to drop a depth-charge in the path of the submarine and hope you time it right.

The real problem with Sub is that you are unlikely to get very far without first enduring long practice sessions. This would be fine (the same is true of Protek's game), but the Romik display doesn't exactly tempt you to spend hours in front of the machine.

If you have a 48K machine, you can happily give this program a miss. 16K owners who are prepared to put in a lot of practice may go overboard for it.