The game has three modes. In the easy mode, you just shoot flying ducks. In the medium mode, there is a blue bird that shall NOT be shot. Otherwise, you will lose the game. In the hard mode, there are two blue birds.
A little trick is that you will get better chance of shoot ducks by put the target ahead of the duck path. It has a global scoring system. So, get the highest point as possible as you can. Enjoy it.