Not bad. Works smoothly and it does what you're describing it to be. You're definitely on the right track.
One suggestion I have is to maybe make the bullets or enemies a bit bigger, or make the time between shooting a little shorter. I felt a bit restrained as I fired the bullets. I do recognize that part of the fun is needing to accurately shoot these enemies however, so I'll leave it as a mild suggestion.
Have you thought of bosses? That could be fun to have in the game. :]
Keep up the good work! I'll definitely play the final version.