anchor: Contact:getPositions
  Returns the contact points of the two colliding fixtures. There can be one or two points.
  x1, y1, x2, y2 = Contact:getPositions()
  x1 number The x coordinate of the first contact point.
  y1 number The y coordinate of the first contact point.
  x2 number The x coordinate of the second contact point.
  y2 number The y coordinate of the second contact point.