             window.clearInterval @field_player
             @field_player = window.setInterval(@field_player_proc, @step_delay)
 
-      doReverseStep: ->
-          if irule = @inverse_rule
-            for i in [0...@step_size]
-              @gol.untransform irule
-            @generation -= @step_size
-            @updateCanvas()
-            @update_time()
-            @recordFrame()
-          else
-            alert "Rule is not reversible"
-            @stopPlayer()
-
       update_time: ->
           @time_display.innerHTML = "" + @generation  if @time_display
 

        E("stable-sub-rules").innerHTML = ""
        if rule[0] isnt 0
          @ruleset = Rules.stabilize_vacuum rule
          E("stablize-rule").checked = false
          E("rule-stabilization-pane").style.visibility = "visible"
          @show_rule_stabilization()

            @doStepRuleset @step_size
            @showRulesetPhase()
          else
            @doStepSimpleRule @step_size
            
          if @spaceship_catcher? and @generation >= @spaceship_catcher.reseed_period
            @do_clear()
