anchor: World:queryBoundingBox
  Calls a function for each fixture inside the specified area by searching for any overlapping bounding box (Fixture:getBoundingBox).
  World:queryBoundingBox( topLeftX, topLeftY, bottomRightX, bottomRightY, callback )
  topLeftX number The x position of the top-left point.
  topLeftY number The y position of the top-left point.
  bottomRightX number The x position of the bottom-right point.
  bottomRightY number The y position of the bottom-right point.
  callback function This function gets passed one argument, the fixture, and should return a boolean. The search will continue if it is true or stop if it is false.