Sweet and simple!
At first I thought the art was a bit too barren, but I saw it was a stylistic choice rather than something done out of laziness or lack of talent. I learned to like the minimalist style pretty quickly, and it really meshed well with the smooth animation.
I don't usually see that much life in symbol-based animation, but you definitely pulled it off well. There was some good secondary action on bits like the ball catching, and everything was really smooth. You also synced it with the music beautifully, and everything felt on beat. The only animation I didn't like very much was the bird's eye shot of Pi Clock walking, then that being reused a few seconds later.
Stylistically the one problem I saw was that some of the background elements were done with the brush tool, and some were done with the line tool. Those two elements didn't quite gel with each other, but it wasn't too detracting.
Your story was very sweet, and like everything else in this animation; simple. I was sincerely surprised to see a Clock Flash without some wacked out twist at the end, but that surprise was a pleasant one. You told the story succinctly without any unnecessary exposition, and nothing was lost on the audience.
Sorry for the wall of text, but I've spent most of today watching the animations my fellow students have been making so I'm a bit critical minded. Great work on this Flash, and congrats on the award and front page!