Very nice theme! The atmosphere really resembles a calm night on an open crop field. The corn stalks falling down made the arena kind of chaotic at times but it only added to the boss fight.
I was not a fan of how you lose the ability to move when you shoot since you have to move to dodge the boss' attacks. A crosshair/reticle would also help a lot since I kept missing the UFO. Overall, it has some fun elements but needs a bit more polish/playtesting.