Moving the mouse within the area of the mask will show different light paths.
You can click and drag the mask to different positions.

Clicking the area outside the mask will show what happens to light emitted at that location.
You can draw an object with the mouse by clicking and dragging.  The image of your drawing will be shown. (example)

Multiple Reflections from two plane mirrors
A game to play with a mirror.

Your suggestions are highly appreciated! Please click hwang@phy03.phy.ntnu.edu.tw

Author：Fu-Kwun Hwang, Dept. of physics, National Taiwan Normal University