Monument Valley is free - you should download it right now.
It's a pared back puzzler with gorgeous graphics and the kind of level of difficulty our brains can handle these days - ie it's very easy. Simple touch controls move around Escher-like mazes and you can take screenshots to show how fancy your phone is.
The game is so good, it randomly appeared in House of Cards - mostly we feel because Kevin Spacey likes games and he figured the president would probably play something fairly easy in his downtime. He also routinely slayed folks in Black Ops in his basement.
Weirdly enough, this actually wasn't paid for product placement - Netflix has an interesting attitude to real-world items in that they just appear, without the need for any cash to change hands. It's almost like their shows actually exist in normal life where products are everywhere...
Anyway, if you're on iOS Monument Valley is totally free right now, so why not use that saving to get the extra DLC puzzles.
Click here to download.