"The Professor Layton series ("Reiton-kyōju series" (レイトン教授シリーズ) is a puzzle video game series for the Nintendo DS, currently consisting of four games and one film. At least two more games and at least one more film are due for 2010/2011. Level 5 has also discussed that a third trilogy is in the works. The first three games are about Professor Layton and Luke's adventures together and their eventual parting of ways. The next three games and the film are prequels and are about how Luke and Layton met and their "original" adventures. Although only two of the games are available outside of Japan, Level 5 has stated that eventually the other games and films will be localized. The games are developed by Nintendo and Level-5.
Each title is based in a series of puzzles and mysteries given by the citizens of towns that the main characters visit. It is not necessary to solve all the puzzles to progress, but some are mandatory and at certain points in the game a minimum number of puzzles must be solved before the story will continue."
Source: Wikipedia, "Professor_Layton_(series)", available under the CC-BY-SA License.