This game is hella fun... and hella hard. Though most of the difficulty is from me trying to get used to the control scheme, I am TERRIBLE at mouse+keyboard setups.
The main complaint I have is that stages take way too long and often overstay their welcome. If the stages' length were cut by like, half or 1/3 then things would flow over much smoother. Also having more varied enemy patterns would be nice. (Also, bullets render under the player. You do not want this in a STG.)
That aside though I still enjoyed the gameplay, everything came together nicely and it was satisfying to FINALLY beat the boss and win. Good work!