It was a bit hard to see if I was hit by enemy bullets or if I’m damaging the boss. Probably would help, if there was any kind of visual or audio feedback and the health bar was green and red for example. But I like this “thought of war” style of boss fight. Also, the enemies and attack patterns are quite elaborate for a game created in such a short time, nicely done!
(Also good that you decided to post some screenshots, those were the reason I even found your game)