On the surface, and in the initial few levels, the game appears to be quite tame; there are only a few small enemies peppering the play field, and they are easily vaporized. As each wave is vanquished a new one begins, almost immediately, containing even more enemies than the wave before it. Small round enemies pave way for large round enemies, which beget small round enemies in increasing number.
Control is with the mouse: Movement of your square is restricted to the horizontal; press the mouse button to shooot.
To aid in your quest for square dominance over circle shapes, enemies will occassionally drop valuable power-ups: red shield upgrades, yellow weapon upgrades, and white 1-ups. Collect every power-up you can, because you will need them as you venture deeper into the game play.
Similar strategies to games of Pang will help with this one, too. In later levels, the big round circles will each yield an army or two. It is best to divide and conquer rather than an all-out blast fest. And blast fest you will get if you play it just right ...and oh, how satisfying it is. =)
Lots of eye candy and a nice techno soundtrack to boot. This one's a keeper. Cheers, Tonypa!