Thanks to everyone who enjoyed it!
Yoyo8dude, in fact I'm already working on a second version that will feature a "Story mode", with rooms and levels to complete and enemy snakes.
Does this work with social bookmarking? Let's suppose I lock my game to Kongregate, and someone links to this page in Facebook. When someone else follows Facebook's link, Fb serves a frameset with this page and a small bar at the top, but the URL has "facebook.com" as its domain name. Would the game be locked if "facebook.com" is not in my list?