Interesting idea!
I like the inherent challenge from trying to balance the two goals.
You can generate a lot of power, but you'll be killing a bunch of birds!
I also like the addition of wind. It forces you to spin the blades so you can't just keep still all the time.
It was hard to tell when a bird was exactly killed, which made it feel unfair when I suddenly lost a heart.
Once you get a hang of it, the game is really fun.