Space Jack doesn't really have much going for it; someone should tell Powerhouse that simply combining two different types of bad game into one title doesn't make it worth buying.
In the first part of this dreary effort, you have to pilot your flying saucer through space to reach your destination. At the top of the screen appears a chart showing your position relative to the planet. You can move and fire in all four directions, shooting the various fluffy aliens which fly around trying to stamp on your head. If you just keep your finger on the fire button and charge to the right, though, you'll complete this part of the game with very little effort. The next bit is a badly-designed platforms-and-ladders bit in which you steer your spacesuited figure through the alien landscape, searching out air cannisters and radioactive eggs (uh?), and avoiding squishy aliens which look like third-rate rejects from Trap Door.
There's supposed to be a secret third level to the game, but the insert gloats that you'll have to find out about it yourself. Boo hoo hoo. I don't think I'll bother, thank you very much.
Pretty scabby combination of space shoot-'em-up and platforms-and-ladders.