Brian Age is one of those games that make you feel good after playing it.

User Rating: 7.5 | Brain Age: Train Your Brain in Minutes a Day! DS
It is a great game to entertain yourself for a few hours with. It forces you to think back to the 3rd grade and how to do simple math problems and reading out load, yet they always seem to have at least one question that you don't get. Charting your brain age gives you a goal to shoot for(20 is the best, sadly I'm 22) The only bad thing about the game is that sometimes the screen doesn't read your number right and makes you wrong. But it doesn't happen that often so, nothing to worry about. Also i wish there were more games on it cause once you beat them all down, you have no more to do. Sudoku was a great part to it though. There are many, many games of sudoku, on all different levels. That in itself should keep you busy and thinking for a couple hours. Yet you can only do so much math, reading, and sudoku before you get tired of it. Overall a very fun game that will preoccupy you have many hours.