In Super Mario Bros., Princess Toadstool of the Mushroom Kingdom has been kidnapped by Bowser, the evil king of the Koopas. Former plumbers Mario and Luigi have been sent to rescue to her and restore peace to the kingdom. They must make their way over land, under ground, and through the sea, in eight worlds divided into four levels each. On their journey, they face a variety of enemies, including Goombas, Koopa Troopas, and Bullet Bills, which can be defeated by jumping directly on them. At the end of each world, the brothers come face to face with Bowser, who must be stopped before the quest can continue.
Power-ups play an integral part in Super Mario Bros. When Mario jumps and hits a question mark block from underneath, an item is revealed. This could be a coin, mushroom, fire flower, or star. The mushroom is the game's most important item -- it makes Mario grow to over twice his normal size and strength, giving him the ability to break bricks with his jump-punch. It also allows him to be hit once without losing a life. Once Mario is in this "super" state, he can collect a fire flower that lets him shoot fireballs. Stars provide temporary invincibility, and 100 coins earn you an extra life.