anchor: love.mousemoved
  Callback function triggered when the mouse is moved.
  love.mousemoved( x, y, dx, dy, istouch )
  x number The mouse position on the x-axis.
  y number The mouse position on the y-axis.
  dx number The amount moved along the x-axis since the last time love.mousemoved was called.
  dy number The amount moved along the y-axis since the last time love.mousemoved was called.
  istouch boolean True if the mouse button press originated from a touchscreen touch-press.