Light Blocks, Dark Tower
From the Super Mario Wiki
Light Blocks, Dark Tower, or Rock-Candy Mines-4, is the fourth course of Rock-Candy Mines in New Super Mario Bros. U. It is unlocked via completion of Grinding-Stone Tower or Shifting-Floor Cave, and its own completion opens the path to a blue ! Switch, a spot where a Bubble Baby Yoshi resides, a green Toad House, and the level Walking Piranha Plants!.
The course takes place underground, and the main gimmicks are large Light Blocks that periodically shift between on and off. The course is also entirely vertical, and Swoopers are prominent enemies in the course.
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