We continuously capture information through our eyes, a huge amount that the brain has to process. Optical illusions happen when what we perceive does not match with what is real. What is interesting is that although we know that what we perceive is not real, we continue perceiving it as our brain is “programmed” to interpret it. In this video you can see a few illusions:
Fortunately the pieces of a puzzle do not have this effect …. but at times you think that you can not advance solving a puzzle and later, magically you find easily new matches that before seemed impossible to find.