[Custom Feature Question] Rock wall Sliding Feature

def Kernel.pbSlideOnRock(event=nil)
  if $game_player.direction==2
  event = $game_player if !event
  return if !event
  $PokemonGlobal.sliding = true
  direction    = event.direction
  oldwalkanime = event.walk_anime
  event.straighten
  event.walk_anime = false
  loop do
    pbSEPlay("eb_ground2")
    $scene.spriteset.addUserAnimation(DUSTBROWN_ANIMATION_ID,event.x,event.y,true,1)
    break if !PBTerrain.isRock?(pbGetTerrainTag(event))
      event.move_forward
    while event.moving?
      Graphics.update
      Input.update
      pbUpdateSceneMap
    end
  end
  event.center(event.x,event.y)
  event.straighten
  event.walk_anime = oldwalkanime
  $PokemonGlobal.sliding = false
  end
end

  def PBTerrain.isRock?(tag)
    return tag==PBTerrain::Rock
  end

# Show grass rustle animation, and auto-move the player over waterfalls and ice
Events.onStepTakenFieldMovement+=proc {|sender,e|
  event = e[0] # Get the event affected by field movement
  if $scene.is_a?(Scene_Map)
    currentTag = pbGetTerrainTag(event)
    facingTag=Kernel.pbFacingTerrainTag
    if PBTerrain.isJustGrass?(pbGetTerrainTag(event,true)) && event.character_name != "nil"
      $scene.spriteset.addUserAnimation(GRASS_ANIMATION_ID,event.x,event.y,true,1)
    elsif event==$game_player
      if currentTag==PBTerrain::WaterfallCrest
        # Descend waterfall, but only if this event is the player
        Kernel.pbDescendWaterfall(event)
      elsif PBTerrain.isIce?(currentTag) && !$PokemonGlobal.sliding
        Kernel.pbSlideOnIce(event)
      [B][I][U]elsif PBTerrain.isRock?(currentTag) && !$PokemonGlobal.sliding[/U][/I][/B]
        [B][I][U]Kernel.pbSlideOnRock(event)[/U][/I][/B]
      end
    end
  end
}