Hexagons

I really like this spinner made of hexagons rotating inside each other. Pure CSS animation, based on the following formula that I calculated :

For an hexagon rotated of an angle A in an another hexagon of a side length L (so that the vertexes of the first always touch the edges of the second), the side length of the rotated hexagon is equal to cos(A)*(L-tan(A/2)*L/sqrt(3)).