I like the pen drop effect. It might be worth detecting the browser as when I read the "put your finger on the screen" my hand actually moved to my laptop screen. Then I realized it was probably for a mobile device and laughed as I used the mouse.
Very nice! Reminds me of an early version FiftyThree's Paper! (<a href="http://www.fiftythree.com/paper" rel="nofollow">http://www.fiftythree.com/paper</a>)
Quick bug report: X and Y are about 20% too high in mobile safari. Also crashes mobile safari frequently.<p>Otherwise, fun. I like the pen drop effect.