This game is good, the movement, the explosions, and the hitboxes feel great. I liked the parallax scrolling, it really effects the immersion, and the game manages to fell great even without screenshake.
I think the player should meet the first boss earlier, I was almost to quit, thimking the enemy waves would just restart. I also noticed that staying on the bottom center with the green 3-projectiles kills most of the enemies before they can hit you.
Overall, I think this game woyld be better on mobile phones instead than PCs, but it's still good on PC ;)
P.S. The high score doesn't save when you quit.