15. Shape Shift HD (iPad only)

Shape Shift HD provides you with a glittering screen filled with colored shapes, tasking you with swapping the shape icons to create clusters of similar colors. That’s no-tutorial-needed simple, and it only grows slightly more complicated when time bombs start showing up around the fourth level. It still makes for a fun and relaxing game, although those pop-up ads for other Backflip Studios games might get to you after awhile.