You probably know Backflip Studios from its many popular titles on the App Store already, but Shape Shift is a relatively new title from Julian Farrior's company. It's a puzzle game, sort of in the vein of Bejeweled, with a grid of icons that you can switch around to match up four or more in a row. The catch is that you can only switch icons of the same shape, but you're trying to match up colors, so the game consists of moving around shapes to line up the various colors.
It's interesting -- definitely a new mechanic from anything I've seen, and it's addictive enough to stay compelling for a while. One little twist is that you can switch "gems" without making a match, so there's a lot of potential for chaining up moves. But in classic mode at least (there's also a Zen mode for peaceful matching), there are bombs and other obstacles to match your way past.
Game Center integration is included, of course, and the game's presentation and polish are nothing less than what you'd expect from Backflip these days. Plus, according to the company's model, both the iPhone and the iPad versions are free and ad-supported, allowing you to clear out the ads with just one simple in-app purchase. Shape Shift is an excellent puzzle game and another great title in Backflip's growing lineup.