Curling is a team sport in which stones are slid across a sheet of ice towards a target area. Teams of four compete to accumulate the most points, scored by sliding granite stones across the length of the ice and positioning them closest to the center of a painted target (the "house"). The trajectory and speed of the stone's movement is influenced by teammates sweeping the ice surface ahead of the stone with curling brooms. Curling involves a great deal of strategy in terms of selecting the right types of shots to make in order to outmaneuver the opposing team. The sport has been an official part of the Winter Olympics since 1998.