This is, quite simply, the best game on the Nintendo DS.
The puzzles are genuinely challenging and worryingly addictive, the interface is clean and user-friendly, and the life span and replay value of the game is fantastic!
It is, however, quite a difficult game (so the more "intellectual" gamer will get much more from this game); I wouldn't recommend it if you're impatient or looking for a "casual" game!
The game has four different gameplay modes;
The "story mode." In this, you must help Dr. Reiner Knizier on his journey around the world: in each location there is a "problem" which you must help Dr. Reiner solve and, for doing so, he'll reward you with money and medals!
These "problems" are puzzles (brainbenders!); there is one puzzle in each location and there are 5 difficulty levels for each puzzle (that's 80 puzzles (which constantly change, so you'll never play exactly the same puzzle twice))!
To complete a puzzle, you must obtain (at least) a bronze medal for completing it. Doing so will earn money (the amount will vary depending on which medal you earned), which will allow you to "buy" the next difficulty level or to travel to another, previously unvisited, location.
Once you've "bought" a city, you can travel to it whenever you please for free, and you can replay levels you've "bought" for free, too. Also, you're not forced to buy the cities or difficulty levels in any particular order (although the more difficult levels are more expensive, and some cities are more expensive than others).
Earning money is easy enough, too, so you'll rarely be frustrated because you can't afford to go where you want to (Dr. Reiner will give out money for "persistance" (if you keep retrying a puzzle) and for setting "very high" scores)!
On your first attempt at a puzzle, you will be given an interactive tutorial, so that you know exactly what to do. Once you've attempted the level once, you will no longer need to replay the tutorial (although you can choose to, if you wish)
Play the cities from "World Tour" 'randomly' to set high scores! You can choose from a 4 Game, 8 Game or 16 Game session and play them in any of the 5 difficulty levels.
Once you've chosen a session and a difficulty level, you'll play through 4, 8 or 16 'randomly' selected puzzles, and aim to set as high a score as possible!
You can view the Top 10 "High Scores" from the leaderboard for each category and difficulty level, too!
You can save any specific puzzles you come across during the "World Tour" and then replay them later from the "Puzzle Bank"!
You can store up to 20 puzzles on each user profile.
"DS Download Play"
You can "share" (send and recieve) saved puzzles with your friends using "DS Download Play"!