This is one of my earliest color optical illusions. There is no yellow or green in the diamond shapes, just vertical black lines! (If you don’t believe it, use a eyedropper tool to check it.)

## Possible Impossible Cube

Is it possible to 3D print an impossible cube ? Here is a way to do it… After all, it’s all about perspective!

Source: Wolfram Community

## A Neat Geometrical Illusion: The Scintillating Starburst

As you maybe know, I am an expert in optical illusions… So, I would like to show you one of my oldest illusions I created in the 90s. In the picture **you may see ghost-like dark radial beams**. This illusion is a variant of the Herman’s scintillating grid illusion. I designed this illusion just by turning 45 degrees the Herman grid and then by applying a polar transformation.

Continue reading “A Neat Geometrical Illusion: The Scintillating Starburst”

## Exterior Angles

In a polygon, an **exterior angle** is formed by a side and an extension of an adjacent side. The sum of exterior angles in any convex polygon always adds up to 360 degrees, as shown in the 2 visual proofs below. Therefore, for all equiangular polygons, the measure of one exterior angle is equal to 360 divided by the number of sides in the polygon.

## Shortest Path on a Cube

Source: https://twitter.com/panlepan/status/1138686590216298497?s=20 by @panlepan

## Impossible Structure

Perpetual Escher’s waterfall

## Six Points on a Circle

Take 6 points on a circle such that every second edge (green chords) has length equal to the radius of the circle. Then the midpoints of the other three sides of the cyclic hexagon form an equilateral triangle.

Read more: https://www.archimedes-lab.org/2-Sunday_puzzle_43.html

## Geometric Passe-muraille

A 3D regular hexahedron solid (cube) passing through a 2D plane:

## Puzzle Creation for Associations

For 20 years, Archimedes Lab has created visual puzzles for the association RMT (Rallye Mathématique Transalpin). You can use them for your personal projects or for your math class. Enjoy!

Depuis plus de 20 ans, Archimedes Lab crée des puzzles – qui sont utilisés comme des attestations – pour l’association RMT (Rallye Mathématique Transalpin). Merci de respecter les copyrights. Amusez-vous bien!

Association RMT: http://www.armtint.org

## Magic Topology!

Can you alter this figure-eight-shaped pastry in order to thread the stick into the second loop? Obviously, you cannot unthread the stick from the pastry nor cut the pastry in any way!

The trick is explained in my book: “Impossible Folding Puzzles and Other Mathematical Paradoxes” available on Amazon: https://amazon.com/dp/0486493512/?tag=archimelabpuz-20