Level 0

Level 0 is a hidden level on bloons 3. You can find it if you Click the previous page button on the first page of levels. It is a normal level in bloons 3 with just 1 bloon, but if you pop that 1 bloon with an activation dart, you'll unlock an expansion pack in bloons 3 called Alternate Universe. Also, you will come face to face with the portal guardian...