GravityChicken manages to be two things, in equal doses - incredibly annoying and incredibly compelling. Your mission is to navigate a chicken around 40 levels full of spikes, holes and all sorts of enemies. The interesting part? You can flip gravity to aid the chicken in her quest to pick up golden eggs.
It reminds me of a PC game, VVVVVV which offers the same sort of game mechanics. GravityChicken's not quite as hideously difficult as VVVVVV and it's certainly prettier to look at, but it's got that same sort of vibe to it. The difficulty lies in the chicken's limitations. She can move through the use of the left and right arrow icons but it takes deft fingers to do this at the same time as flipping gravity. It takes a lot of practice to succeed at many of the levels and you'll find yourself repeating stages frequently.
It would have been nice to have seen some form of OpenFeint or GameCenter support here as it would have been great to compare progress with friends. However, the main satisfaction lies in simply surviving. Many harsh words might be uttered at your iPhone during play but you can't help but feel smug when you finally complete a particularly awkward stage. The developers have done a good job of keeping you keen, as every now and then a level will be relatively simple. It'll make you think that you're finally a master of the game, then it'll throw another awkward level at you. You'll keep playing, though. It's got that frustrating element about it that means you'll refuse to be beaten.
Don't play GravityChicken if you've got anger management issues or you want a soothing, relaxing game. If you want an inexpensive and challenging puzzler, this is a perfect game to purchase.