I like that the strength of the beam does get affected the further away you are from the ground. The rockets turning red is also a great choice of conveying its lifetime to the player.
The UFO could be slightly smaller, it seems a bit too big relative to the screen. The rockets also shouldn’t spawn from the bottom like it’s coming out from under the ground past the sheep, it doesn’t make sense.
All in all, I had some fun playing it, and it’s a decent game. Keep it up!