(not a review!)
I love puzzle games on the DS! I have Tetris too! I've never played Brain Age 1, so this is about the game I do have!
There's options for training and quick play. Training means you have your own file and 'brain age' (how old your brain is - the number gets 'younger' the better you get.)
There's several exersizes, including; finding the signs for equations very quickly, finding the right amount of change, playing piano, remembering how many blocks fall into each box - simple things that are surprisingly hard! My favorite game is Virus Buster, which is a mix of Dr. Mario and Tetris. It's the game you play to relax. I'm pretty good at it :)
Since this isn't a review, just a "thing I like", I won't give a rating or anything. I'm *not* (oops forgot that) the biggest or best gamer, so I probably won't do reviews of games ^_^ I want to do an article on Mario too, but I don't know facts about his games through the years...quick! To wikipedia!