Super Mario Bros. 2 is a 2D side-scrolling platform game. The objective of the game is to navigate the player's character through the dream world Subcon and defeat the main antagonist Wart. The player takes on the roles of the four protagonists of the game: Mario, Luigi, Toad, and Princess Toadstool. All four characters can run, jump, and climb ladders or vines, but each character possesses a unique strength that causes them to be controlled differently. For example, Luigi can jump the highest and Princess Toadstool can jump the farthest. The player chooses the character to use before the start of each level. Unlike other Mario games, the characters cannot defeat enemies by jumping on them; but they can stand on, ride on, and jump from the enemies. Instead, the character picks up and throws objects at the enemies, or throws the enemies away, to defeat them. These objects include vegetables plucked from the ground, or other enemies.
The game consists of twenty different levels across the seven themed 'worlds' comprising Subcon. Each world has a particular theme that dictates the obstacles and enemies encountered in its levels, such as desert areas with dangerous quicksand and snowy areas with slippery surfaces. Levels contain multiple sections or rooms that are connected via doors or ladders. Some rooms are accessible by entering certain jars. Magic potions found in each level are used to temporarily access 'Sub-space', an inverted area where the player can collect coins and Mushrooms that increase the character's maximum health. In addition, certain jars, when entered in Sub-space, will warp the player to later worlds, skipping levels altogether. Other items available include cherries, which are collected in order to acquire a Starman; and the POW block, which can be used to quickly destroy all enemies visible on the screen.
The player starts Super Mario Bros. 2 with three extra lives, which are lost each time the player's character loses all health from enemy or hazard damage or when the character falls off the screen. The player can replenish health by collecting floating hearts that appear upon defeating a certain number of enemies. The player will receive a game over upon losing all lives, though the player may continue up to twice in one game. Additional extra lives may be obtained by collecting hidden 1-Up Mushrooms or by using the coins collected from Sub-space to win the slot machine minigame played between levels.
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