A small collection of some of the best optical illusions (also known as visual illusions) and visual phenomena I have stumbled upon.

"Checkershadow Illusion":

Perhaps the most powerful optical illusion I have found.

The squares marked A and B are the same shade of gray.

Credit:

Checkershadow Illusion copyrighted by Edward H. Adelson

Proof:

Use our ZoomView freeware tool to zoom in and see the colors of the squares.  They are both the same color.  Here is Edward Adelson's proof and an explanation.  For the ultimate proof, save and edit the image yourself!

"Lilac Chaser":

Stare at the center.  The purple turns green and eventually disappear!

Credit:

Lilac Chaser by Michael Bach and Jeremy Hinton.

"Dongurakokko" Illusion:

This is also known as "the donguri wave" illusion.

The donguri (acorns) appear to wave.  Any motion you sense is an illusion.

Credit:

Dongurakokko is copyrighted by Akiyoshi Kitaoka.

"Fraser Spiral":

Also known as the false spiral, the twisted cord illusion, and Fraser's Spiral.

The "cords" do not spiral.  Use your finger or mouse to help.

Proof:

Use your finger or mouse pointer to help guide your eye around the circles.  Without aid, your eye will easily "slip" and jump to the next lower "cord", incorrectly following a spiral that does not exist.

Additionally, Michael Bach offers proof (click the link and mouse over his image to see).

Credit:

The Fraser Spiral was created by James Fraser.  Parts of James Fraser's original paper ("A New Visual Illusion of Direction", British Journal of Psychology 2: 307-337, 1908.) have been made available by Hervé Varenneere.

"Waterways" Illusion:

The blue squares are not slanted.

Proof:

Scroll this page and cut off the image with your browser window.  Warning:  This illusion is so powerful it will still trick you unless you can cut off the image accurately.

Credit:

Waterways is copyrighted by Akiyoshi Kitaoka.

"Undokai" Illusion:

The rectangles make perfect circles that are not connected.

Proof:

Use your finger or mouse pointer as a guide to follow the circles.

Credit:

Undokai is copyrighted by Akiyoshi Kitaoka.

"Expanding Golden Cushion" Illusion:

The image appears to bulge and expand.  It may even appear to physically stick outwards at you.

Credit:

Expanding Golden Cushion is copyrighted by Akiyoshi Kitaoka.

"Shoals" Illusion:

A subtle effect; The top and bottom appear to move left and right.

Credit:

Shoals is copyrighted by Akiyoshi Kitaoka.

"Expanding Snakes" Illusion:

Look around the image and the center appears to expand.

Credit:

Expanding Snakes is copyrighted by Akiyoshi Kitaoka.

"Radial Gradient" Illusion:

The image appears to come toward you slowly, as you move your eyes around.

Credit:

Radial Gradient is copyrighted by Feng Yuan.

Suggestions?

Know any optical illusions we should add?  If so, please contact us or post in our forums.

External Links:

• Optical Illusions & Visual Phenomena (Michael Bach)
• Akiyoshi's illusion pages
• Optical illusion (Wikipedia)
• All Optical illusions pages (Wikipedia)
• Optical phenomenon (Wikipedia)
• All Optical phenomena pages (Wikipedia)

About the Author:  I am Matthew Doucette of Xona Games, an award-winning, team-of-two indie studio concentrating on "intense retro" games (Xbox LIVE, PSN, WiiWare, and Windows PC). We've released Decimation X (XBLIG), a 1-4 player shmup, #1 best selling and #1 top rated XBLIG in Japan. We're working on Duality ZF (XBLA), a groundbreaking 1-4 player shmup, which placed #1 in Canada and #5 in the world in Microsoft's Dream Build Play 2010 contest. It features dual play, the ability to control two fighters at once, and a massively upgradable 32-stage spread/laser weapon system. 4 player dual play allows up to eight fighters at once.  Many of these features are never before seen shoot'em up firsts. Both games feature beautiful electronic Imphenzia soundtracks.  Help spread the word with our official dualityzf.com and decimationx.com websites.

P.S. Watch out for Score Rush (official website scorerush.com), another 1-4 player shmup. Coming soon to XBLIG.

*Shmup also known as: shoot'em up, 2D shooter, scrolling shooter, space shooter, spaceship shooter, retro shooter, etc.