You have been chosen to destroy the invincible Termination Planet, which threatens the universe. Only one weak spot has been found, an exhaust vent, and you are given only one chance. You must steer your X-winged fighter along the trench, avoiding the alien ships and lasers. When you get close to the vent, your attack computer is engaged, and you must position the sights over the small hole, fire and retreat.
The graphics are nothing special in Trench (written by Phil Wilkes), though they do the job sufficiently. You can see the eponymous trench - which scrolls quite nicely - your X-winged fighter, alien ships and firing lasers. At the bottom of the screen is a message centre which tells you how many miles to go and, after the game, what happened, e.g. 'Hit by laser'.
You can hear an engine noise all the time, the pitch of which varies with your altitude. There are other sound effects for when alien ships close in, lasers fire, for being killed, and for the run-up to the end of the trench before missile-release.
There's a joystick option, Clares or BBC but once you've selected keyboard or joystick you can't change, so if you enter Clares joystick when you have BBC you have to reload the game. There are nine levels of play. Increasing the difficulty level, makes the trench longer. There's no sound on or off option, or game pause.
The first few times I played Trench I found it much too hard, being hit by lasers all the time. I stuck with it, though, and now I can place a missile, though I usually get blown up along with the Termination Planet. Success seems to be random, depending on whether a laser hits you or not.
Trench is nothing special, with standard graphics, though quite good sound, and I feel it is too difficult.