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A Boost Block is a block used in New Super Mario Bros. U. Boost Blocks can be used only in multiplayer mode, and to use one, a player must tap the Wii U GamePad screen. Boost Blocks are intended to serve as platforms to help Mario and co. progress in the level. There are other uses for Boost Blocks, such as placing them above character's heads to prevent falling objects like Thwomps to harm them or stopping enemies from exiting a pipe. If a player steps on a Boost Block while a symbol is shown, the block releases three coins while filling the Boost Star meter, though if a player steps on a block without a symbol on it, the Boost Star meter will disappear, no matter how full the meter was before disappearing. If a player steps on 10 Boost Blocks with a symbol shown in a row, a Boost Star will appear, and the player using the GamePad can tap it to gain Boost Star power.
If a player gets 99 lives, the boost blocks are shrunk into small, square Mini Boost Blocks, making them more difficult to land on. However, the Boost Star meter becomes easier to fill because the playing-card symbols does not disappear while Mini Boost Blocks are onscreen.
Boost Block designs
Names in other languages