Unexpected 3-D with CSS. Pretty cool.
Say what you want about skeuomorphism being passé. Bullshit.
As someone noted recently (who’s blog post I’ve forgotten), Apple didn’t get rid of skeuomorphism at all in iOS 7—it’s layers and layers of UI behaving like semi-transparent/frosted glass, and the simulated physics of animations continue to be refined (like when you drag iMessages up and down with your finger).