Shuplyak's hidden faces optical illusion in a fun online puzzle.

"Hidden Faces" is a fun psychology class puzzle for desktop computers, laptops and tablets, which may be played in the web browser. Sort the hidden picture.
The Psychology Knowledge Board include 40 square pieces to rotate and finish the picture of impossible figures illusion. It is part of the Interactive Mind Studies educational tools.

This fun education class may answer some of the following questions:

• How there are hidden faces in a drawing?