Strata is a puzzle game like none that I've ever played, and since I spend a good deal of my time specifically looking for unique puzzle games on the App Store, that's saying something. There are no fun little characters, no bright lights or flashy graphics; it's just colorful ribbons and some soothing music, and it's a fantastic way to unwind.
Your objective in Strata is to layer colored ribbons over a grid in such a way as to color the blocks underneath. You can lay your ribbons in two directions, and when two ribbons overlap the top ribbon color is the one that gets carried through to the block below. Each puzzle grid consists of a square with anywhere from four to 36 blocks, and as you might imagine, the difficulty increases exponentially with each grid size.
Depending on the number of colors involved, puzzles can take just seconds or several minutes to figure out, but the point here isn't to rush through each challenge. The game rewards you for taking your time and thinking out each ribbon placement ahead of time. Scoring a "Perfect" rating means layering the ribbons the exact correct way with no re-dos. This is a lot more difficult than it might sound.
The music of Strata is perfect for the type of relaxing puzzle experience the game provides. Soothing tunes ripple and sway as with each ribbon you place and when you mess up, the music will squawk in an unappealing fashion, alerting you to the error.
Strata costs US$2.99, and there are currently level packs available for a couple of extra bucks. There are also "Hint packs" you can purchase to help you through the trickier spots, but I'd highly recommend ignoring this option, since the feeling of accomplishment when you best a challenging puzzle is really what the game is all about.