Bullethell games are always fun! I didn't read the part that you have to tag the bullets with your amplifier so the first few levels took a while (my mistake!), but perhaps there could also be something in-game that tells you how it works that you have to tag the bullets with the beam things on the side of your ship to change the color. The speed of the ship is good relative to the speed of bullets so you have enough time to dodge and movement works. I like that the ship color indicates what color bullets you need to kill it. Overall, very nicely done!
Here are some bugs that I encountered:
If you die while rewinding, the bullets can still go through the amplifier and kills the ships so you pass the level and can play again.
I couldn't figure out how to restart the level / gameplay after a loss so I had to restart the whole game for that.