Click and hold your mouse down to manipulate the location of the light source, let go to let go. Use the sliders to change the light sources properties and the objects properties. To turn on debug mode, click T on your keyboard Two colored arrows and a blue line will appear wherever your mouse is. The Green Arrow points always to the light source. The Red Arrow points always to the object. The Blue Line is always oriented the same way as the shadow. You control the x and z axis using your mouse.