The mission style, which can be played in a marathon or time trial mode, starts off like a regular game of Tetris, though simply clearing lines isn't enough to advance you. While your playfield resides on the lower screen, the top screen presents you with specific tasks that you must complete in order to advance. Sometimes you'll need to clear a number of lines with a single, specific piece, sometimes you'll need to clear one line without rotating any pieces--whatever the challenge, if you don't do it in a timely manner, the game will punish you by adding lines to the bottom of the field. Though superb for sharpening your Tetris chops, it can also be confusing, as some of the task descriptions aren't completely concise, and some of the tasks themselves can just be totally frustrating to actually pull off.
Lastly, there's catch, which only barely resembles Tetris--though, unlike the touch games, catch just isn't much fun. You're given a four-block core that you can move and rotate at will on the lower screen, while pieces slowly descend from the top screen. When they reach the lower screen, you can attach them to your core just by letting them touch down. The goal here is to create solid four-by-four sets of blocks, which when created will explode, simultaneously advancing your score and bringing the size of your cluster back down to a manageable one. Things get complicated as more pieces start to fall along with block-destroying obstacles, but the pacing never really speeds up adequately, and the whole thing just starts to feel like a grind.
A few of the modes mentioned have multiplayer components as well, and you can play standard, mission, and push games against other players locally--best of all, the other players don't even need to have copies of the game. Tetris DS features some of the best game sharing we've seen on the Nintendo DS, allowing up to 10 people to participate in massive, competitive games of Tetris. The local multiplayer is also one of the few places in Tetris DS where you can actually make modifications to the rules, most notably the ability to form between two teams of five and five teams of two, and the ability to turn on or off items. The items, which can have positive and negative effects ranging from giving you nothing but straight pieces for a limited time to preventing an opponent from rotating their pieces, can be picked up by clearing lines that contains special flashing blocks, and can be stored until you activate them with the X button.
The local multiplayer is hands down the best thing going for Tetris DS, which should say a lot about the quality of the game's online multiplayer. Yes, Tetris DS is online-enabled, though it's kind of underwhelming, since there are only three different modes, none of which you can modify. There's standard two-player, two-player push, and standard four-player with items. You want to play a two-player game, but with items? Or maybe you want to play a three-player game? With Tetris DS, you're out of luck. For what it's worth, the online experience worked well enough, but by comparison to the local multiplayer offered, it just seems poorly realized.
Tetris DS has a lot going for it--plenty of gameplay modes, amazing game sharing, and online play--which makes it all the more disappointing that it contains no "pure" Tetris experience, and features a weak selection of online gameplay modes. But still, it's Tetris, one of the most popular and significant puzzle games ever, and some of the magic that put it in such a venerable position still manages to shine through.