     if @changers[category] then @changers[category].finish()
     @changers[category] = changer
 
-  next: ->
+  to_next: ->
     unless @alg.at_end()
       this.add_changer('move', @alg.next_move().show_do(@world3d))
 
-  prev: ->
+  to_prev: ->
     unless @alg.at_start()
       this.add_changer('move', @alg.prev_move().show_undo(@world3d))
 

    this.animate()


  # this function is executed on each animation frame
  animate: ->
    now = (new Date()).getTime()


      when 'pause'
        @alg.stop()
      when 'next'
        this.to_next()
      when 'prev'
        this.to_prev()
      when 'reset'
        this.to_start()

