this is extremely fun to play with and smoothly done.

If you dig this, please also see the work of Kumi Yamashita, who does similar shadow artwork with letters and shapes, but in real life.

http://kumiyamashita.com/

some stuff is super hard to believe, like:

http://kumiyamashita.com/images/BUILDING-BLOCKS-FOR-WEB.jpg

other artists working in this genre too:

http://www.designer-daily.com/remarkable-shadow-art-405