Blank Bubble Sort Puzzle

How To Play:
- In the beginning, only balls from top are colored.
- Tap any tube to move the top ball from one tube to another.
- You can only move a ball on top of another ball if both of them have the same color or if the tube is empty.
- Once you move the ball, the ball behind will uncover its color.
- If you get stuck, you can use free moves, which allows you to move a ball on top of another ball even if they have DIFFERENT color.

Features:
* 12 tubes colors
* 21 backgrounds
* 3 difficulty level