Good, especially for Flash
You usually see these kind of physics rigs with EXEs or Java applets, i haven't seen one in flash yet. There is something exactly like this, i'm shure you've seen it, it's called Sodaplay, you make suuff just like this.
Other than that this was pretty awesome, it was fun to make different shapes and whatnot and drag them around. It was also fun making huge boulders fall on litle stick people :D