In response to feedback I’ve made the following tweaks to my game:

• the cue guideline is no longer locked while aiming
• the cue guideline now has a chevron pattern to show direction
• you must click a button to spot the next planet after each shot (this prevents a player from finding the perfect spot and sticking there.)

You can play the updated version here: http://scratch.mit.edu/projects/10575019/

The original entry is here: http://www.ludumdare.com/compo/minild-42/?action=preview&uid=11312