Just had a quick go at work.
Couple of things
I can use shield after I had died so shield is appearing without player sprite.
The player is jumping on the edges when trying to keep in bounds
(this is probably because your player control events are happening after your keep in bounds events. If you change the order around this should stop.)
There is not enough feedback when I am hit.
The primary fire sprites could do with a little beefing up graphics wise, just a little, they are hard to see against some of the backgrounds.
The player hit box appears to be front weighted, (very accurate to the front of the ship but missing for much of the back of the sprite )
normally for these types of games you want a hit box that is smaller (maybe half the size) of the player sprite and bang in the middle.
I would dearly love to see the bosses animated….
But , regardless, what you have achieved there is fantastic,
I very much look forward to having a proper go when I get home...