Defy Gravity is an interesting arcade puzzle game that looks for all the world like a platformer, and plays like one for about the first three seconds. Then the twist comes in - your player can shoot gravity fields that can either attract or repel objects. The most obvious uses for these are to enable your character to jump longer / higher, reach places your jumping alone can't get you to, and make enemies get out of the way. There are quite a few uses for your gravity wells though - it's up to you to experiment and find out how best to use them. On most levels (as far as I can see) there is more than one way to achieve your goals, so the game has quite a flexible approach.
Defy Gravity looks nice and sounds good, and plays very well - animation is smooth, the controls are responsive (mouse + keyboard), the levels are well designed and the game will certainly give you a challenge. Some levels look completely impossible to start with, but eventually you begin to work out strategies for getting past even the most imposing of obstacles.
If you like puzzle games with an element of action to them, you'll definitely enjoy Defy Gravity.
(To be honest I wasn't entirely sure what the plot had to do with it all, but that's in the best tradition of arcade games!)
Defy Gravity Website