Pretty fun, I got to about 512 or so. Graphics look nice and I liked how the background and rock graphics would change. Nice music too. I thought the fog actually did work quite well with the concept as it gives you the additional challenge of trying to see the rock faintly within the fog and responding early.
In case you didn't know, you could make a "Play Again" button like this instead of "Refresh to Play Again" in Easel:
RaisedButton(Main, backgroundColor=Color:Primary) { "Play Again" }
In either case, great job!