Swaying Ghost House
From the Super Mario Wiki
Swaying Ghost House, or Frosted Glacier-Ghost House, is the Ghost House level of Frosted Glacier in New Super Mario Bros. U. It is unlocked via completion of Scaling the Mountainside or Icicle Caverns, and its own completion unlocks Wendy's Shifting Castle. The level also has a secret exit that unlocks Fliprus Lake.
As every other ghost house, the place is inhabited by Boos. A unique feature of the level is that the rooms and objects slowly swing back and forth constantly, sometimes moves along with the screen when scrolled. Many P-Switches are found in this level.
The secret exit is in the same room the third Star Coin is located, just through the door in the far-right of the room.
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