Not Bad, Well...
This is a good attempt at making a game. Your animation isn't bad at all, I especially like the explosions when either the boss or you die yourself. The only thing I would suggest in any kind of future endeavor in games are health bars for yourself and the enemy. Or at the very least white out the forms when they detect collisions so the player can know when a hit has landed.
Music was okay but as the games not long not many people wont hear past 15 seconds. A theme song or something similar could keep people company on the title screen, and sound effects while shooting and exploding would make it a little more engaging.
If you improve these small things, and increase the difficulty level or at least the duration, u could be looking at a decent start of a gmae.