Bonus Levels in Where's My Perry

Many of you don't know there are bonus levels in Where's My Perry. However, these bonus levels can greatly boost your scores! So let me tell you something about the bonus levels in the game Where's My Perry.

First of all, How to find BONUS levels?

--Well, the answer is thar if you find three collectible files in a set you'll unlock a bonus level. You can find these secret stages in the "collection" screen, available from the main menu.

Secondly, how do I know that it is a bonus level?

--Each stage features a balloon (with a man's face, for some reason which is really weird for me) which floats up towards a vacuum pipe at the top of the level. You need to ensure the balloon's safety by digging paths, pushing it with water and building icy barriers.