Super Mario 64

This game begins with a letter from Princess Peach inviting Mario to come to her castle for a cake she has baked for him. When Mario gets there he finds out that Bowser has invaded the castle and imprisoned the Princess and her servants in the castle using the power of the 120 power stars. Many of the castle's paintings are portals to other realms, in which Bowser's minions keep watch over the stars. Mario searches for the portals, entering them to recover the stars. As he finds more stars, he can reach new places in the castle.