I'd make several changes:
#1 Fix the F-11 message. Is this an IE thing? Do a browser detect, and display the right message.
#2 Get rid of the share on Twitter links at the end. just tacky.
#3 Get rid of the countdown. 30s break is cool, but countdown display speeds time up. Make the countdown hidden. If the user presses spacebar before 30s is up, should say "try harder" and reset the countdown.
#4 get rid of the cursing wasn't that funny
Anyways, I really liked this, especially the music and the white space.