It was fun, but not enough to hold my attention for too long, it's too simple.
I think you may be onto a winner with the concept, I just feel.. there's nothing here I've not seen before, y'know?
There's plenty of physics variable sandbox play toy things out there, most much more entertaining and interactive than this. I will grant you that this probably takes a level of scripting expertise that I don't have the drive or effort to achieve. But it's just lacking appeal at the moment.
It's the thing in the shop that you pick up because it's interesting, and once you see what it is, you put it down and never think of it again.
Keep working, this as far as I'm concerned, is an experiment en route to you building a fun and interesting flash game. Nothing more.