It's at the top of the thread.
Map Difficulty - Legendary Checkpoints - 4 The abbreviation BT at the beginning of this level's title stands for "Bunny Track" BT levels are...
Difficulty - Legendary Iron Checkpoints - None The abbreviation BT at the beginning of this level's title stands for "Bunny Track" BT levels are...
Map Difficulty - Normal Checkpoints - 5 The abbreviation BT at the beginning of this level's title stands for "Bunny Track" BT levels are...