Platforms: iOS, Android
VOI is a minimalistic puzzle game that will drive you insane. There are 88 levels and on each, you are given a seemingly simple shape to recreate using other shapes. The pieces are all black but when they overlap, they become white. The shapes will always be ones you wouldn't think would together make the given shape, and that's where it gets interesting. There is no time limit, which means you might end up frustrated for long periods of time trying to get through a level.
However, there is a “hint” option, which annoyingly doesn't provide you the hint. It solves the entire thing for you after making you watch an advertisement, ugh. I would recommend not pressing on “hint” unless you absolutely cannot figure out what to do.
VOI is perfect for working your brain when you don't have much to do. It builds puzzle-solving skills, which could come in use someday. It's also fun to play and finally being able to solve a level you were stuck in is highly satisfying.