Got 50000+ score, I had to go after that ;)
Here's my two cents as feedback: I'd enjoy bigger bullets that move faster and an increased rate of fire (at least 2 or 3 fold haha). If this makes the game too easy give the asteroids 1 to 3 HP randomly.
Also, it might be worth it to ramp up the difficulty based on your current score. Start out easier then increase asteroid spawn rate (or asteroid move speed or blackhole gravity strength, you get the idea). I feel like this might already be slightly implemented, but I couldn't really tell 😅