.. .
................................(cf, 10, 10, 0)
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Man Climbing Stairs

From: LABLaughsClean

Source: http://www.lablaughs.com/clean_toon.php?id=C19970505

Perpetually ascending staircase. 
How can the man go up all the time and come back 
to the same place over and over? 

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. .
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Wavy Dominos

From: LABLaughsClean
At: LABLaughs@LABLaughs.com on 1/20/2006

Source:
http://www.lablaughs.com
/clean_toon.php?id=C19970511
 

Warped Square? 
There are no curved lines in this figure.

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Rotating dot whirlpool
From: igiggle
on 1/25/2006
Source:
http://www.skytopia.com/project/illusion/illusion.html

Wow! Try staring at this for more than 5 seconds
without going crazy. Then try following it round!
Curves constantly die out and then re-evolve as
part of another curve. 

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Skewed Lines

From: igiggle
on 1/25/2006
Source:
http://www.skytopia.com/project/illusion/illusion.html

All these tracks look as though they've come from a broken down 
railway track, but in actual fact, they are perfectly parallel! To 
prove they really are parallel, watch the small 'hairs' gradually 
disappear. You will see the lines as how you would expect them to be.

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A Bulge

From: igiggle
on 1/25/2006
Source:
http://www.skytopia.com/project/illusion/illusion.html

Created by Akiyoshi Kitaoka, the lines in this picture 
below are completely parallel would you believe?

Visit his Anomalous motion illusions web site
for more illusions in this style.

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The drawing

Paris In The Springtime

From: igiggle
on 1/25/2006
Source:
http://www.skytopia.com/project/illusion/illusion.html

What does this simple green signpost say?
Guess again.

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The Glowing Core

From: igiggle
on 1/25/2006
Source:
http://www.skytopia.com/project/illusion/illusion.html

Look into the centre (white point) and stare for a while. How many colours can you
see altogether in the object? You should see a purplish circle... and the 4 rotating
'wings' are tinted green. Make sure you always keep focused on the centre.
Once you've done this, read on...

Are those four wings really green? Amazingly, they are exactly the same colour as
the circle inside. Don't believe me? Well try following one of the wings round.
You'll see that the colour matches the inner circle perfectly.


NB. The faster the circle rotates, the better the illusion will work.  Unfortunately, Explorer has great trouble displaying GIF animations faster than about 10 frames per second, so I suggest saving the anim and then using an external such as Irfanview. Visit www.irfanview.com for more details.
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Wheel of Confusion

From: igiggle
on 1/25/2006
Source:
http://www.skytopia.com/project/illusion/illusion.html
 

Wheel of Confusion
Which way is the wheel turning!?
Focus on the red dots and follow them round... it appears to be 
rotating anti-clockwise. However, if you follow the yellow dots round 
instead, the whole wheel will be turning the other way! - clockwise!

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Find Your Blind Spot
comes
From: igiggle
on 1/25/2006
Source: http://www.skytopia.com/project/illusion/illusion.html










Another popular one - and quite unnerving if you've never seen it before...  Close your left and eye and just focus your right eye on the tiny cross. At some point the big circle will disappear as it crosses your 'blind spot'. If you can't see this effect, then try sitting closer/further from the screen.

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Ambiguity

From:
igiggle

on
1/25/2006

Source:
http://www.skytopia.com/project/illusion/illusion.html

There's certainly something very ambiguous
about which way this is meant to be up...

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or