This is really cool, and seems like it will be even more fun once you've collected a bit more data.
One minor usability tweak: having the slider "snap" to the hour doesn't quite feel right. The end result is that the ball is never actually under my cursor, which feels broken. Might be more usable if the mall always stayed with your cursor, but snapped back to the nearest hour when you let go.
Nice stuff though - it will be cool to see how you evolve this.