At this point, I think the whole world knows what Tetris is. This is a puzzle game involving falling pieces that you try to arrange in lines.
With Tetris DS they provide multiple versions so you can keep your brain sharp. First comes the basic version - you can play this vs the computer, or solitaire in a line clear mode or a 200-line-at-once mode.
With the push game, the computer is stacking from below while you add in blocks from up above. You are trying to create lines faster than the computer does.
In catch, you have a "sticky" block you navigate in a stream of blocks. You glue these blocks to yourself from all sides, trying to form a solid cube.
We particularly enjoy touch. This creates a gigantic tower of tetris pieces. You have to slide them left and right to get them to fall into a pattern. It's really quite challenging!
Puzzle mode gives you specific pieces and then a board layout. You have to figure out how to drop those specific pieces in order to clear the board.
Tetris is one of those great time killers that can easily fill five minutes while you wait in line, or a longer period if you get involved in a long session. I definitely make sure to have a Tetris or Puyo Pop game for each of my handheld game systems.
There's even multiplayer versions in here if you have friends with a DS you'd like to play with. The game keeps track of all your high scores in case you want to post them to boards. There are options in here to enable the fast-down you see in many tetris games. One thing you should do immediately is turn off the "ghost piece"! This is a grey image of where the tetris piece will land based on its current position. It makes the game way too easy, and while it can be helpful for young kids who have never seen Tetris before, it takes all the challenge out of the game for others.
If you already have a tetris game, then I'm not sure you really need a second. However if you don't yet have a Tetris system for your DS, then definitely consider this version. You get a number of variations, and each will keep you entertained for quite a while - plus keep your mind sharp!