You must guide the orb through the level to the goal. You do this by simply clicking on the orb and drag it to the green goal zone. But the orb must not hit a wall or you'll have to start again. You don't always have to carry the orb, you can drop it by double clicking. The orb is not the only thing that you can carry. There are crates that you can pick up and drop on switches. The orb can also change color. Depending on the color you can do different things. The orb will change when it hits color changers.