optical illusion

Wow
(and be sure to click on the ‘proof’ link…)

btw, this is a great example of the frailties of perception…
magicians and con men (from salesmen to psychics) exploit weaknesses in perception and cognition, therefore “mind hacking” is a good description of what they do…
or perhaps “reality hacking”, since our faith in our own perception and cognition is the foundation of how we establish and experience reality…