I love the retro style of it like it's from the nes or the snes, the luck based factor of the game makes it really special instead of you always win. You could add maybe a timer that shows on the top but instead of normal seconds it's milliseconds so the player doesn't fully know when it happens.

I like the graphics. I agree with the other comments that the game is too luck-based, and thus the player's action becomes inconsequential to the outcome. Maybe you could add a lightning graphic just in the cloud, that is constantly moving horizontally in a certain pattern, and it will only strike down at random timing. (Like in the real life, the lightning appears inside the cloud too; only once in a while it strikes down.) This way, the player can see the pattern and try to choose different birds that's far away from the potential lightning strike. If you feel that's too easy, then may be try two lightnings moving independently at different speed and changing direction at random time; and there are clouds (could be moving randomly)  in front of the lightning and thus the lightning may be obscured by these clouds sometimes. The movement of the potential lightning will give the player some kind of pattern to anticipate and the clouds in front could momentarily take away the player's ability to anticipate, but at least the player can make their action accordingly. Hope this makes sense.

The only thing I don't like is that it is really luck based. other than that I really like the art, it's a cool idea, and it's pretty fun!

The game is short but entertaining, the graphics are good, and the two-button concept is well implemented. The only downside I see is that winning seems to depend on luck, because I don't know what pattern the beam follows to kill a duck. Otherwise, it's fine