The Hermann grid illusion is an optical illusion reported by Ludimar Hermann in 1870. The illusion is characterized by ghostlike gray blobs perceived at the intersections of a white grid on a black background. But I discovered that when you turn the grid 45 degrees an additional visual illusion appears: you may see a swarming of orthogonal darker lines.

The animated version of the illusion is more striking. With the power of your mind, you can even make the geometrical pattern rotate clockwise or counter-clockwise (but when the pattern rotates clockwise, you will see the illusive radial beams rotate counter-clockwise, and vice-versa).

This animated version from Youtube features a rotating white pattern on a black background followed by a rotating black pattern on a white background. The scintillating effect is more apparent on the second variant.

I have experimented with many pattern variants that produce illusive radial beams, as showcased below…