YP Shadow - Version 1.0 YP Shadow simulates a light source projecting the shadow of an opaque body on a screen. Using the mouse, it is easy to change the position and the size of the light source, the position and the size of the opaque body, and the position of the screen. YP Shadow draws the rays of light used to mark the boundaries of the umbra and the penumbra, and it displays the shadow as it appears on the