This is cool! Only real issue I had was that the movement felt a little slow when setting the initial course of the probe.  The music is great, and I really like the changes of the planet faces when you enter / leave their gravitational fields :)

I like the innovative idea. I think that since you have all of this time, you should add more levels, make them progressively harder, and add some particle effects (like when you crash into planets), and make the game more fast past.