It's hard not to recommend this, given that I made a 7 cent profit from buying the game then selling the cards... getting paid to play a game is never wrong. :-)
But even ignoring that, I had a surprisingly good time with it. Defy Gravity is your basic puzzle platformer where you have to use an unusual mechanic to navigate levels. In this case, you can shoot gravity fields that attract you or repel you and activate a shield that lets you ignore all gravity fields. By mixing these, you can sort of rocket-jump-grapple-hook your way through levels. Some timed jumping and obstacles that sometimes are and sometimes are not affected by the gravity are there to stop your progress.
In the words of a wise man, you're going to die. A lot. The game takes delight in throwing stuff in your way at just the wrong moment. But at the same time, it's surprisingly forgiving with how you swing around the level and you can often brute force your way through tight spots. "Hectic" is not a word you usually associate with puzzlers, but Defy Gravity can get pretty hectic -- and that's when it's arguably at its most fun. For me it hits just the right balance between frustration and challenge.
The graphics and sound are absolutely nothing special, but in terms of pure gameplay, this is value for money even when it's not 90% off. When it is, of course, it's a no-brainer, just get it. :-)