Nice tutorial and here is the online game: <a href="http://demo.nothingtohide.cc/" rel="nofollow">http://demo.nothingtohide.cc/</a><p>I remember seeing a nice web page where you could play around with lights and walls in real time and see the results. Something like a lights and shadows on-line real time simulation, but I can't remember the address and couldn't find it by searching. Anyone knows the page I'm talking about?