Goal Door (Mario vs. Donkey Kong series)
From the Super Mario Wiki
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Goal Doors (also known as M Doors, exit doors, or simply doors) are the main objective in every non-boss level of most games from the Mario vs. Donkey Kong series. Mini Marios must enter these doors to end the level.
Goal Doors debut as end-of-level targets in Mario vs. Donkey Kong 2: March of the Minis, where they appear as curved, yellow-colored jambs with an "M" symbol imprinted on them. In Mario vs. Donkey Kong: Minis March Again!, they received slight changes: the "M" symbol is absent, and the door has a slight pink border. However, in Mario vs. Donkey Kong: Mini-Land Mayhem!, they got completely changed: in single-door levels, the door is red with golden border. Unlike the previous games, the door will be closed if the minis aren't brought in after each other in a small amount of time, trapping some minis behind.
In addition, Mini-Land Mayhem! features Multi-Door levels, where each Goal Door is assigned to only one of the playable characters—Mini Mario, Mini Toad, Mini Peach, Mini Donkey Kong, or Mini Pauline. They are colored red, blue, pink, yellow or green, in respect to each character. Each mini must be brought to its own Goal Door. Unlike levels with one Goal Door, there is no time limit in between how long it takes for one mini to enter its door. Both the regular and assigned Goal Doors reappear with the same use in Mario vs. Donkey Kong: Tipping Stars, along with a light green Mini Luigi door.
Mario vs. Donkey Kong: Mini-Land Mayhem!