This game is the first game for the BBC which is protected by the infamous Lenslok. Let me just briefly explain how this works.
When the game is loaded, a garbled message appears. You then stick this little piece of plastic prism in front of it, do a few things, squint your eyes, swear a bit and hey presto, you can read a two character code which must be entered to play the actual game.
The principle behind this is that, even if you copy the tape with an Amstrad tape-to-tape machine, you can't play it because you can't decode the code. Elaborate stuff... but is it really worth it?
The game is, in fact, an accurate conversion of a simple shoot-'em-up of the same name which emerged in the arcades about five years ago. It basically involves a base which may be moved laterally and firing at a variety of meanies floating around above in the darkness of space.
There is also a bonus stage where you have to dock. In fact, this is a very accurate conversion indeed. The trouble is, the game is so hideously outdated. The graphics are reasonable but the tiridulously simple games concept, minimal sound effects and its slow speed makes Moon Cresta a very boring game which couldn't be rescued by the incentive of winning the original arcade machine.