Here's the thing about Strata, a beautiful mobile puzzle game created by Graveck: it can be tough to wrap your head around. On the surface it seems simple enough, as all you have to do is swipe to lay fabric-like strips of color. Once you sit down and see even the simplest of puzzles, though, you'll realize how the game creates a nightmare out of order and sequence. Not the bad kind of nightmare, of course. The good kind that makes you want to sit and stare until you figure everything out.