the gameplay is similar to previous games in the series but introduces new features such as a new control system and more levels in the upgrade system for weapons. it follows ratchet and clank's adventure through a fictional universe to defeat a robotic villain, dr. nefarious, who intends to destroy all organic life. characters such as dr. nefarious and sasha, a cazar starship captain who helps ratchet throughout the game, are introduced, and a number of characters return from the original "ratchet & clank".