A promising start but lots of things to improve.
I did not enjoy the controls, with the turn left control that worked improperly (seemed to be a pivot point issue), but mostly having to keep the mouse button down to shoot all the time can get tiring : unless you add some bosses where it can be advantageous not to fire during some phases, you might as well make shooting automatic.
Moving the ship with the mouse was kind of tedious as it is slow, and the boss is faster. However, that's a matter of taste, if you want to make a game where you have to be careful and anticipate a lot, go for it.
The hitbox on the boss seemed really small, was it only the middle red dot? Some feedback when you damage the boss would be nice, ideally a flicker/white flash/explosion fx etc. Thankfully there was a health bar at the top, because of this small hitbox and the speed /scarcity of player bullets made it hard to keep hoping the boss would die.
Oh, and you might want to restrict player movement to the screen and not allow it to go out of bounds.
On the good side, the music was great, and the background with the stars was a nice touch.
Finally, I'm curious about the lore you cooked up for this.... how does the angel metatron relate to some flowers? Hoping to see more of this later on!