Great game, poor instruction
I think most people who say it's hard is because they think you need to pull back the slingshot to shoot. This is because in the instructions it tells them to do so. A change to the instructions or at least an edit in the Author comment would help.
Just click behind the slingshot to shoot, you don't need to pull the sling back! If you do it that way you can shoot faster and it becomes a lot easier.
Other than that it's a good game, great presentation....