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This wobbly spinner also called a "rattleback" features a physics defying unpredictability. Which makes it perfect for equally unsure decision making. Includes one 3¾" long rattle back and one 4½" wide decision disc.

This mechanism demonstrates a surprising way to generate an ellipse by using a four-bar linkage. The shape of the ellipse can be defined by the path the intersection point of the two crossing bars follows. This fact is analogous to another neat way…


"Amina Allen took a close look at the stellated dodecahedron inside an icosahedron, and found 10 squashed cubes, each with six rhombic faces that are all ""fat"" Richert-Penrose tiles. Has no one ever noticed before? Even Marc Pelletier never…

It's a Klein bottle 3D printed in resin in a pendent with a mobius strip tag.

Text by: David G. Haskell,
Illustrations by: Ellen Litwiller

Physical gift a small E link puzzle and a puzzle postcard.
Paper 'Multiplication by Superposition' -

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This is a rolling block puzzle. Roll the block from the start location to the end location. Avoid the obstacles in your path, and don't roll the block over its beveled edge. It will take some decaflops to get to the finish!

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