New Background, advanced orbital mechanics

Hi all,

Later this week I will be posting an update to Disturb the Universe. The main items in the update are:

• better background to more easily detect movement, 
• true elliptical orbits for planets
• a guiding arrow showing the player which way to the goal
• a level preview which shows where the goal is at the beginning of each playthrough
• better level generation

I look forward to showing you all the progress and improvements!