Algodoo

No need to run Algodoo. Just grab the spotlight with your Move Tool and move it closer to the dark mystery picture. Your spotlight will reveal the hidden image! You can move the light around any area of the picture.

You can also change the focal distance of the light beam by left-clicking on the spotlight. Then right-click and move your cursor to Material. In the Material list, you can change the Friction slider which will change the focal length of the light beam. Try it!

BTW - This scene will lag with slow computers. Sorry about that.