       else
         a = 0
         b = opacity
-      @_shaders[anchor].left[i].style.opacity  = a
-      @_shaders[anchor].right[i].style.opacity = b
+      @_shaders[anchor].left[n].style.opacity  = a
+      @_shaders[anchor].right[n].style.opacity = b
     else
       if angle < 0
         a = 0

  # wouldn't be called due to no animation taking place. This method reasons if
  # movement has taken place, preventing this pitfall of transition listeners.
  _isIdenticalOperation: (op) ->
    return true  unless @lastOp.fn
    return false if @lastOp.reset
    (return false if @lastOp[key] isnt op[key]) for key in ['angle', 'anchor', 'fn']
    (return false if v isnt @lastOp.options[k] and k isnt 'callback') for k, v of op.options

      else
        a = opacity
        b = 0
      @_shaders[anchor].top[n].style.opacity    = a
      @_shaders[anchor].bottom[n].style.opacity = b


  # This method shows the requested stage element and sets a reference to it as
