The Idea of the game is quite simple, your mission is to hit the target with your canon. You decide how much you want to "charge" your canon, you must calibrate with much precision to hit the target. But that's not all, the wind changes after every shot so you must include the power of the wind in your calculations.
You can also upload your score to a global highscore list. You can see the top 10 highscores in the game menu.