The main goal of the game is to get through 10 levels before your timer runs down to zero. To climb through the levels, you need to hit the fire button when the ship is in the black space. If the ship hits the playfield, you will be sent down a few lines and 25000 points will be taken from the timer. If you get to the top of the level, you will receive 200000 points and ascend to the next level. Make it through all 10 levels and you escape, getting a score that you can brag to your friends about. Screw up, and you get zero… and cooked!

http://www.atariage.com/forums/topic/168157-passthrough-2600/