Have you seen any optical dillusions?

Never heard of a "dillusion" ... had to look it up.

Dillusion \'di 'lu-zhen\
1 a : an idea regarding the self or persons or objects outside the self that is deliberately constructed and professed to be believed in order to delude others, the truth or falsity of which idea is either truthfully or falsely believed to be within one's own control.
1 b : the recognition that a perception or idea is an illusion but the recognition is coupled with the delusion that the true nature of the perception or idea therefore is known or knowable.
1 c : the deliberate posturing with apparent conviction that a perception or idea that is true and which appears to be true is a mirage, or the reverse, that a perception or idea that is false and is known to be false is true, until one completely succeeds in fooling oneself.
2 : a trancelike state of rumination and confusion in which one is compulsed continually to argue with oneself but create a win-win outcome.
3 : the merging of confusing thoughts involving the deception of self or others with dilution, diffusion, dissolution, disillusion, and disassociation.
4 : a stop without a farmhouse near between the woods and frozen lake the darkest evening of the year.
5 : the object of an apostrophe.
6 : hallucination that one can spell.