Fairly basic stuff, I'm afraid. Even the in-game plot gives me no material whatsoever to base some entertaining drivel on.
It has something to do with aliens and trapping them, using your forcefield-
If you close off an area, this becomes unusable to the aliens and knocks off a few more per cent in the quest to close them down. Your ship can only move along the exosed edge of the closed area, never within it. Dead simple.
It is complicated slightly by the fact that the big main alien you are trying to trap has lots of attendant little aliens which do their best to harass you. This isn't so bad because you are only vulnerable when trying to close off a new area of the screen, but these guys move very fast so you have to be quick about closing off the screen area.
Grey squares will appear in the open play area, and sometimes disappear. If you manage to trap one of these while closing off some space then a bonus is revealed - it may be a speed power-up, or the ability to fire jolly impressive laser bolts - these can be used to kill the annoying little aliens.
You get 1,000 points for each 'normal' alien you trap. The bonus for trapping the major alien varies on how little space he is trapped in - the smaller the area, the bigger the bonus.
Trapping the big alien is not the only way of killing him. On some levels, if you collect the bonuses in a certain way you can get a huge gob-
Graphics are all a little boring, looking very much like the kind of uninteresting superfluous detail you get when you have 32 colours but can't think of anything do with them - my mother would have called it 'too busy'. The sound follows trends in being surplus to requirements - a nice soundtrack would have done the trick but the lack of effort has resulted in effects that go all over the place and completely miss the point.
The necessarily repetitive gameplay builds tension in a way that frustrates very quickly and makes you want to go and hit something, rather than making you want to try and beat the thing.
That is about the size of what is really a very basic game. It did well in the arcades, but is less likely to be successful on home formats - there just isn't enough there to warrant spending the kind of money on nothing more than a lot of levels of the same game that get a bit harder every time. Variety does not equate to Volfied.