This section contains a small but interesting visualization of mathematical subjects.

A convex polyhedron is regular if...

Duality of regular polyhedrons: cube and octahedron, icosahedron and dodecahedron, tetrahedron.

Is there a polyhedron, other than the tetrahedron, with any two faces sharing the same edge? Is there a polyhedron with any two vertices connected by the same edge?

Is there a tetrahedron, whose all altitudes’ bases fall beyond its faces?

The cat sits in the middle of a ladder leaning against the wall. What's the trajectory he'll follow if the ladder starts sliding on the floor?

A beautiful astroid curve is a trajectory of a point on a circle, rolling without slipping on the inner side of the circle of four times larger radius.

Jean-Jacques Rousseau and a square of a sum.

A sum of odd numbers.

Illustrative proof of the equivalence of the polygons' equivalency and equidecomposability.

Calculating the sum of triangle angles by paper folding.

How to fold a square sheet of paper to form a triangle whose sides are in the ratio 3:4:5?

How to calculate the sum of a series by folding a sheet of paper?