Super Mario Galaxy 2[a][b] is a platform video game developed and published by Nintendo for the Wii. It was first announced at E3 2009 and is the sequel to 2007's Super Mario Galaxy. It was released worldwide in 2010. The story follows Mario as he pursues the Koopa King, Bowser, into outer space, where he has imprisoned Princess Peach and taken control of the universe using Power Stars and Grand Stars. Mario must travel across various galaxies to recover the Power Stars in order to travel to the center of the universe and rescue Princess Peach.