I have verified that all the physics work correctly in Firefox 3.5.8, and the game is completable. There are several jumps that are only barely possible, and others that are only barely impossible to make.

As people are having some trouble with the first three levels, I've provided a description of the correct path under the "Spoilers" link. Several people that have thought there's a physics bug simply haven't found the right path. There are lots of jumps that almost work in this game.

Unfortunately, the only indication that you've reached the end is that the clock in the upper-right corner stops.