I picked up a used DS for 50$ and I have this game and animal crossing. I'll say this... Animal Crossing is not worth 35$.
However Brainage probably is worth 20$ Who gives a flip what the game is rated? I don't think thier is any nudity and don't think the esrb board has changed the rating via gta SA or Oblivion.
ON to the game.
There are several different modes to start out, there are roughly 100 sodoku puzzles and thats pretty cool. There is another ds game devoted entirley to sudoku and thats probably a better choice if thats what your looking for. This game has a pretty good system for it but is writing intensive.
Another option is daily training. YOu make a profile and take a "Brain Age Test" thats what the main portion of the game revolves around, you taking tests and checking your brain age. The game has about 10 minigames and wants you to play a minigame at least once a day. Then you get a stamp on your calender. If you play at least 3 mini games a day then you get a bigger stamp on your calender. The more stamps the more things you unlock. I must mention you play this game holding the ds vertically and is writing/stylus intensive.
Among the minigames there are quick addition and multiplication... You write in the number with your stylus. A reading aloud activity to test your sylables per second. A Low to High exercise, in which it shows you 4 boxes with varying numbers from 1-10. They flash for a second and you have to order them from lowest to highest.
One of the funner aspects of the game is when you compare your results to others who have accounts on the game. And you have bragging rights over them. I mean just imagine telling your girlfriend how much smarter you are than her?
One portion of the game tells you to draw a picture of random things... like a water facuet or a hippo. Then it shows you the prerendered drawing the game has. Later it will compare you drawing to other people who have drawn the item also. My drawings prettty much suck.
This game incorporates almost all aspects of the ds hardware, stylus, voice, and wireless play. But thats where most people think the game takes a huge dive, as it only has 20X quick multiplication/addition and subtraction. YOu can link up to 12 people and see who gets done faster. Its actually pretty fun requiring only one game cartridge. The only other option is a little downloadable demo.
Cons : Can be repetitive, limited multiplayer, requires you to be on the top of your game and use your brain
Pros : 20$, Fun addictive minigames, Sudoku, Requires you to use your brain.
Summary anylasis : If you have no friends to borrow this game from you had better buy it. Its not a game meant to sit down with and play for an hour, its a game to sit down and play 20 minutes for weeks at a time. So if its your type of game...