Complex sentence: Redjack had several different engines implemented into the game, the main engine was rotatory 3D engine used for the main exploration and adventure and then when your character gets into a fight it loads a new engine to fight characters, generally one-on-one.
Split into simpler sentences: Redjack had several different engines implemented into the game, the main engine was rotatory 3D engine, used for the main exploration and adventure. When the character gets into a fight, the game loads a new engine for fighting characters, generally one-on-one.