Thanks so much for your kind words and for the feedback! No worries about the stars. I'm going to make a post-jam adjustment to the coal area when the jam ends -- so that I make the right adjustment, were you attempting to jump up when the coal-shoveler was looking down to shovel coal, or when the smoke was in the air between his view and you? A few players have now told me they were initially trying to go when he shoveled, whereas the game was designed so that the player would go while there was a smoke screen.
The game does have a complete ending, and there is perhaps 1/3 to 1/2 of the game left after the coal shoveler. Thanks again for playing and giving feedback!