You control four spacecraft, trying to save as many people as you can before the world blows up.
Three of these spacecraft are satellites which shoot time reversal beams, controlling the dangerous fissures that erupt from the ever expanding core.
The last spacecraft is a shuttle that beams people from static cities and randomly formed beacons.
Points are only obtained by rescuing people, so you must balance surviving for as long as possible with collecting as many survivors as possible.

Gameplay video: http://www.youtube.com/watch?v=fYm8WC9TV7U