You are the bubble shooter and you have to pop the bubbles. As you shoot them they become smaller and smaller, until eventually they are totally gone.

To do this you have a harpoon which you can use to shoot the bubbles as they bounce over you.

The controls set by default are:

Move Left Left Arrow Key

Move Right Right Arrow Key

Shoot Space Bar

And remember you can change the control keys as you like in the controls option in the game. Just click on the action and press a key to assign to it.