anchor: love.mouse.isDown
  Checks whether a certain mouse button is down.
  
  This function does not detect mouse wheel scrolling; you must use the love.wheelmoved (or love.mousepressed in version 0.9.2 and older) callback for that.
  down = love.mouse.isDown( button, ... )
  button number The index of a button to check. 1 is the primary mouse button, 2 is the secondary mouse button and 3 is the middle button. Further buttons are mouse dependant.
  ... number Additional button numbers to check.
  down boolean True if any specified button is down.