Beauty lost in Difficulty
I'm going to be very frank with this game.
Within the first 10 levels I was awestruck. I've never seen a game with a concept so simple yet so beautiful. I love the way you draw out the trails of each individual spheres, leaving behind the wonderous patterns which are actually observable in real austronomy.
However, onward past the first 10 levels, the awestruck was replaced by simple frustration and ugly trial & error. I no longer can grasp the concept which the levels expect of me. Am I to now play dodge with flying rocks of destruction for survival? Am I to forget the beautiful patters and the simplicity which I saw earlier? Am I to now slave at the game, tries after tries, waiting in eternity for that 0 moment? Your lack of game testing and concept development sowed the disastrous patterns of game play, which continued till the exhaustion of the players. For me that was my 696th attempt; I was far from the end (Lv 24).
I must say, I'm not the brightest person around, but I'm sure the majority here shares my disappointment towards the impossibility of many levels in this game.
Rants over, now to suggestions:
Make your map zoomable. The universe is big, it's huge, GIGANTIC! The out of bound limitation chokes the control of the spheres while attempting to dodge at the same time. If the spheres needs more space to orbit then give it the space. I believe the theme is "orbit" not, "within boundries".
Your planets... especially the moons have awkward physic behavior. Given all identical mass their flight path should resemble a similar pattern. This is not seen during the "Hair Pin" level where the moons randomly attract to eachother resulting in early self-destruction before I can do a thing.
The spheres, including the sun, also run into the problem of have too much gravitational pull on eachother. While I can understand the difficulty of setting the correct forces between the moon and the planet, etc, and your point of the universe build on gravitational pulls. If the attraction between the planets out weight the attraction of the sun easilly, then the players can't correct planet's flight path. Conversely, if the attraction between the sun and the planets are too strong, the players have no method of preventing unnecessary attractions. While some suggested "parking the sun", I believe it is better to assign a key which temperarily disables the sun when pressed.
The speed of the planets. Visually, it's fantastic to be able to see the spheres in motion at the given speed, if they don't hit eachother or fly out that is. Players have very limited responding time to position their sun and to salvage what error they've made. I would suggest a slow down key which 1/2 or 1/4 the progression of the whole game while the players move their sun to the favorable position.
Lastly, when the game pauses due to the player's failure in completing the level, please show the frame where the "fault" has happened. This will greatly help the players repositioning their sun during the next try.
Overall, great ambience to the game; nice bgm and background picture. Margin of error is too small for later levels. Great potential. Should be further developed and modified. Don't forget testing, if you can't do one level under 40 tries, expect some players not getting it under 120. Looking forward to the next version of this game. If there will be one that is.
4/5, 7/10 Good luck.