Ratchet: Deadlocked (known as Ratchet: Gladiator in Europe and Australia) is a 2005 third-person shooter platformer, developed by Insomniac Games and published by Sony Computer Entertainment for the PlayStation 2 as the fourth installment of the Ratchet & Clank series. The game's story begins as Ratchet, Clank, and Al are abducted and forced to compete in "DreadZone", a violent game show in which heroes are forced to kill each other. Ratchet is given a "DeadLock" collar, which will explode if he becomes uncooperative or boring. The three must find a way to deactivate the collars and free the other heroes being held prisoner. Deadlocked was the last Ratchet & Clank game to be rated T, despite the introduction of the E10+ rating earlier that year. It's also the last main series Ratchet & Clank game to be released on PlayStation 2. The gameplay is similar to that of other games in the series, but focuses more on shooter aspects rather than platforming. The player, as Ratchet, fights in DreadZone tournaments across the "Shadow Sector" in the "Solana" Galaxy, with a large variety of weapons. This game was the first in the series to feature cooperative gameplay in a story mode, and also includes an online multiplayer mode. Some vehicles return from previous games, and new ones are introduced. For the first time, Clank (in his typical form) was not a playable character. Deadlocked was met with generally favorable reviews and was a commercial success, selling 2.1 million copies by 2007.