There is a thread of light on the middle and there is a triangle prism, which can be moved by dragging,
and can be rotated by scrolling the mouse. When you put the prism on a path of the light,
the light will deflect or reflect by the edge of the prism. The light includes several wave lengths.
A series of colors will appear in a form of a rainbow. Both refraction rate and the color depend on the wave length.