Your little spaceship gets launched from planet to planet and it breaks one orbit after the other. Grasp a planet, release it at the right moment and get launched and cling to the next planet. Continue as long as you haven't exploded all planets! If you get slung out of the solar system before all planets have exploded, you'll have to play the level again before you can continue.
Hold the left mouse button or the spacebar to hang on to a planet close to you. Then release to destroy the planet and get slung to an eventual next planet.