Now this is really a space adventure and a half! First on the screen you have a choice of battlegrounds (in space that is) some which are fictional (Betelgeuse sounds familiar) some not. The idea is to save the planet in question - to do this you must destroy every other alien ship or base (which are displayed on one of the many scanners) this is the only way to save the planet - however, you only have so many years to complete this in. There is a very useful pamphlet which accompanies the cassette - I advise you to read it, otherwise you might get stuck.
Your weapons include photon torpedoes, lasers, and - wait for it - an antimatter bomb! this will destroy everything on the screen including you if you are unfortunate. But one small thing which I found annoying - the movement is not very quick and while attempting a quick retrofire the aliens got in a few shots (while you type in the commands).
Otherwise, this is an enjoyable game requiring a little patience.