Dudes,
Brain Challenge is very freaking fun.
I highly recommend you download the trial and see if you like it.
The full game has 25 more mini-games that fit into one of the same 5 themes--Logic, Math, Memory, Visual and Focus--as well as some great 'Stress Mode' games that make you play 2 mini-games at once, or complete standard mini-games but with crazy visual distractions like blurring, bugs crawling around on-screen, or multi-coloured streams flashing around.
The multiplayer takes a cue from Wario Ware by dealing you some cards, each representing a mini-game belonging to one of the 5 main themes, and tasking you with getting rid of them by successfully completing the game that comes up. You take turns with up to 3 other people and get more points by answering correctly faster. Once you have nailed 3 in a row, you get a bonus card that lets you swap one game-card for another, or choose one for someone else
(if, say, you notice a person is bad at Math games, you can force them to play that type)
Lastly, the way it keeps track of your scores, progress and stress levels by play, day and even month is really neat. It's fun to compare with Friends on the leaderboard but man the Achievements in this game are a beast. The biggest Gamerscore ones are 100% brain capacity and I think getting an 'A+' on a training session game, and so far my best is only 13% and a 'C'