In Thrust you fly a spaceship behind enemy lines to steal pods which, apparently, will power the more powerful ships of your side, once you make it back alive.
It's an arcade cave flying game. What it sets it apart from games like Scramble is two things: that in this game there is gravity and you have to use your tractor beam to steal a pod. The pod then sort-of connects to your space craft like a trailer, greatly impacting it's flying behaviour, in combination with the gravity.
On higher levels the gravity is reversed, refreshing the challenge.