Good.
After 2000 points though, it's just tedium. It'sn o longer a test of skill, but a test of how much boredom you can stand.
Add increasing difficulty. Maybe aliens that shoot, or just other obstacles.
Your art needs work. The black hole is convincing enough, since you explicitly tel us what that id, but with just 2 parallax swirls you could make a kick ass black hole. Also, the ship should explode or melt, or something when the game is over.
I understand you may be wanting to keep this simple, but I don't think tedium is one of your objectives, so increase the difficulty progressively, if anything.
Add sound.
Good programming overall. Most people don't know how to do gravity, and it's so easy to do. Good job. Maybe you can ad a high score thing to your website so we can see the best of all time, or at least, the players that could stand to sit there for 10 minutes straight weaving left and right.