In "New Super Mario Bros. U," you play as Mario, Luigi, or Princess Peach as they try to rescue Baby Mario from the clutches of Bowser. The gameplay is reminiscent of classic Mario games, with a focus on side-scrolling platforming, power-ups, and precision jumping. The game introduces new power-ups, such as the Flying Squirrel Suit, which allows Mario to glide through the air, and the Super Acorn, which gives Mario a few extra abilities.