World 7-Castle (New Super Mario Bros. Wii)
From the Super Mario Wiki
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In this level, there are numerous Skewers that the player will have to avoid. They all vary in size and speed. Sledge Bros. also make an appearance here. Ludwig von Koopa is fought again here. The fight takes place on three moving platforms which change height at times. Ludwig will fire four navy-blue fireballs, then jump to a nearby platform with flutter jumping. While he is casting his spell is when the player should jump on him.
If the player completes World 7-6, a vine will lead them into a tower of the Castle. If they choose this path, they will be taken into a hidden room of the castle. If the player goes through the pipe in the room, they will be dropped right in front of the door to Ludwig's battle.