lauder, there's more information in The Headless Horseman book forum. If this doesn't help, you might want to check there.
...object is to fill up space with moons to about 75% of space. you click and hold to create a moon. moon cannot touch walls. moons will be destroyed if a fireball hits it while you are creating it. So if it looks like a fireball will hit it, lift your finger off the cursor.
...wait until you see the three fireball moving away from an area and click in the middle of that area. hold as long as you can to make biggest moon possible. keep doing that until space is filled. good luck