Use the mouse to loop Boogas to clear each sector. You need to react quickly but steadily. Since you cannot touch anything in the Void without being damaged, your ship is equipped with an energy tail that trails behind. By circling around things, you create a spatial well that destroys anything in the encircled area. You use this looping technique to get rid of the Boogas. You can also use this looping to destroy anything else in the sector.