Sigma 7 is really rather good. It looks a little like Zaxxon (brilliant semi-3D arcade game) but then goes on to reveal original and entertaining sections.
There isn't much sign of a strong plot-line, but the pleasing gameplay and attractive graphics make up for this.
Sigma 7 is split into three sub-plots, each with a different aim.
At the start (Stage 1) your little space craft can be seen launching off from an impressive mothership and making a flightpath diagonally up the screen.
As soon as the mothership has moved off the screen and you are happily motoring away, on come screaming waves of green aliens that swirl and twirl all over the shop, making flying very hazardous indeed. The obvious solution is to bank left and right, wiping out the aliens as they appear. This is pretty easy to begin with, but soon gets tricky as more appear at a faster rate.
Once these are dispensed with (a fairly easy task on the first levels) another large construction will appear in the top right-hand corner of the screen and work it's way down. Once you get to it, you'll find yourself on Stage 2 which is a little like Pacman in an odd sort of way.
You're in control of a tank-like vehicle which sits on a sort of griddy affair which - initially - has pathways littered with little coloured blobs. By guiding your tank over the pathways you pick up some of the blobs. Others will stay in place (and more of those in a minute). Hampering your progress by running into you are small square aliens that revolve and gang up on you if you're not careful.
Now, after you've collected all the blobs you'll be able to memorise the pattern of the immovable ones. And these will be used in Section 3. Once all the blobs have been eaten, you'll have to battle your way up to the top right of the screen, through all the aliens and on to the next section.
At this point a couple of comments about the graphics wouldn't be too out of place.
Although the 3D is all very nice thank you, there's rather too much attribute clash for my liking and. although it may look quite 'effective' when an alien is being blown to smithereens, we've now been shown that there are ways around the problem. (Dandy, Shadow Skimmer et al). Having said that, the aliens are all very well drawn and they explode in a cloud of smoke, which is a nice touch.
Anyway, back to the game. Section 3 is even stranger than the previous stage. What we have here is a sort of matrix of square buttons drifting in space with some peculiar plant objects floating around the outside. At this point you turn into an object closely resembling another planet of some sort. Here you must push down the buttons on the matrix in the pattern of the fixed dots on Sector 2. Complex eh? No, I didn't understand it either.
All the time you are heckled by something or other that looks a bit like a pyramid which goes around un-pressing all the buttons. It'll also kill you on contact and so is generally to be avoided.
Then once you've completed this bit you go all the way back to the beginning and start again, although the aliens are more unpleasant and things are a bit tougher around.
Really quite nice. Good graphics and varied gameplay make it well worth the cash. Could lack addictiveness.