Right! Get fell in you 'orrible little droids! And you! Get your capacitor polished! Now listen carefully 'cos I'm only going to tell you this once. There's been an unprovoked chemical attack on one of our planets. The Octagon Squad - that's you, stupid! - have been chosen to go in and get out the survivors...
The idea is to move your team around the complex, blocking off exits and entrances to prevent the alien life forms from taking over.
Octagon Squad is a competent strategy game - but it really needs a bit more explanation to help out the first time player.