How to add 8-way moving in a game ?

#==============================================================================
# ＋＋ 8-Direction Characterset Edit ver. 1.01 ＋＋
#  Script by ParaDog
#  http://2d6.parasite.jp/
#------------------------------------------------------------------------------
# Additional 'diagonal' movement is now possible by pushing combinations of the
# vertical and horizontal controls (up & left, etc) simultaneously.
#
# Additional charsets  for the  8-directional movement  are to be stored within
# the "Graphics/Characters" folder, just like the regular charactersets.
#
# Name the new  diagonal movement charactersets  the same  as the regular ones,
# but with a new '_quarter' extension.   As such, you would name the very first
# characterset: 001-Fighter01_quarter.
#------------------------------------------------------------------------------
# Additional notes:
# This system can be used with the 'Dash Characterset Edit' system,  but please
# place this script 'BELOW' the fore-mentioned Dash script for it to work.
#
# As you can combine the two scripts (Dash and 8-Directional), you can also use
# charactersets that show diagonal running action, also stored within the same
# "Graphics/Characters" folder.
#
# Naming the new graphics would require the inclusion of both '_dash' and the 
# '_quarter' extensions as shown here:  001-Fighter01_dash_quarter.
#==============================================================================

#==============================================================================
# ** Game_Player
#------------------------------------------------------------------------------
#  This class handles the player. Its functions include event starting
#  determinants and map scrolling. Refer to "$game_player" for the one
#  instance of this class.
#==============================================================================

class Game_Player < Game_Character
  #--------------------------------------------------------------------------
  # * Frame update
  #--------------------------------------------------------------------------
  alias update_para_quarter update
  def update
    update_para_quarter
    unless moving? or $game_system.map_interpreter.running? or
           @move_route_forcing or $game_temp.message_window_showing
      # If the direction button is pushed, move the player in that direction
      case Input.dir8
      when 1  # Move Lower Left
        move_lower_left
      when 3  # Move Lower Right
        move_lower_right
      when 7  # Move Upper Left
        move_upper_left
      when 9  # Move Upper Right
        move_upper_right
      end
    end
  end
end

#==============================================================================
# ** Sprite_Character
#------------------------------------------------------------------------------
#  This sprite is used to display the character.It observes the Game_Character
#  class and automatically changes sprite conditions.
#==============================================================================

class Sprite_Character < RPG::Sprite
  #--------------------------------------------------------------------------
  # * Frame Update
  #--------------------------------------------------------------------------
  alias update_para_quarter update
  def update
    update_para_quarter
    if @tile_id == 0
      if (@character.direction - 2) % 2 == 1
        # Checking the presence of the diagonal charset
        if quarter_graphic_exist?(@character)
          # Set the diagonal charset
          if character.dash_on and dash_quarter_graphic_exist?(@character)
            @character_name = @character.character_name + "_dash_quarter"
          else
            @character_name = @character.character_name + "_quarter"
          end
          self.bitmap = RPG::Cache.character(@character_name,
            @character.character_hue)
          # Acquire direction
          case @character.direction
            when 1
              n = 0
            when 3
              n = 2
            when 7
              n = 1
            when 9
              n = 3
          end
        else
          @character.direction = @character.sub_direction
          # When the diagonal charset does not exist, direction
          n = (@character.direction - 2) / 2
        end
        # Set original transfer rectangle
        sx = @character.pattern * @cw
        sy = n * @ch
        self.src_rect.set(sx, sy, @cw, @ch)
      else
        self.bitmap = RPG::Cache.character(@character.character_name,
          @character.character_hue)
        # Set original transfer rectangle
        sx = @character.pattern * @cw
        sy = (@character.direction - 2) / 2 * @ch
        self.src_rect.set(sx, sy, @cw, @ch)
      end
    end
  end
  #--------------------------------------------------------------------------
  # * Diagonal Charset?
  #--------------------------------------------------------------------------
  def quarter_graphic_exist?(character)
    # Reading check
    begin
      RPG::Cache.character(character.character_name.to_s + "_quarter", character.character_hue)
    rescue
      return false
    end
    return true
  end
  #--------------------------------------------------------------------------
  # * Dashing Diagonal Charset?
  #--------------------------------------------------------------------------
  def dash_quarter_graphic_exist?(character)
    # Reading check
    begin
      RPG::Cache.character(character.character_name.to_s + "_dash_quarter", character.character_hue)
    rescue
      return false
    end
    return true
  end
end

#==============================================================================
# ** Game_Character
#------------------------------------------------------------------------------
#  This class deals with characters. It's used as a superclass for the
#  Game_Player and Game_Event classes.
#==============================================================================

class Game_Character
  #--------------------------------------------------------------------------
  # * Public Instance Variables
  #--------------------------------------------------------------------------
  attr_accessor   :direction        # direction
  attr_accessor   :sub_direction    # sub_direction
  #--------------------------------------------------------------------------
  # * Move Lower Left
  #--------------------------------------------------------------------------
  def move_lower_left
    # If no direction fix
    unless @direction_fix
      @sub_direction = @direction
      @direction = 1
      # Face left if facing right, and face down if facing up
      @sub_direction = (@sub_direction == 6 ? 4 : @sub_direction == 8 ? 2 : @sub_direction)
    end
      return if pbLedge(-1,1)
      return if pbEndSurf(-1,1)
      return if moving?
    # When a down to left or a left to down course is passable
    if (passable?(@x, @y, 2) and passable?(@x, @y + 1, 4)) or
       (passable?(@x, @y, 4) and passable?(@x - 1, @y, 2))
      # Update coordinates
      @x -= 1
      @y += 1
      # Increase steps
      increase_steps
    end
  end
  #--------------------------------------------------------------------------
  # * Move Lower Right
  #--------------------------------------------------------------------------
  def move_lower_right
    # If no direction fix
    unless @direction_fix
      @sub_direction = @direction
      @direction = 3
      # Face right if facing left, and face down if facing up
      @sub_direction = (@sub_direction == 4 ? 6 : @sub_direction == 8 ? 2 : @sub_direction)
    end
      return if pbLedge(1,1)
      return if pbEndSurf(1,1)
      return if moving?
    # When a down to right or a right to down course is passable
    if (passable?(@x, @y, 2) and passable?(@x, @y + 1, 6)) or
       (passable?(@x, @y, 6) and passable?(@x + 1, @y, 2))
      # Update coordinates
      @x += 1
      @y += 1
      # Increase steps
      increase_steps
    end
  end
  #--------------------------------------------------------------------------
  # * Move Upper Left
  #--------------------------------------------------------------------------
  def move_upper_left
    # If no direction fix
    unless @direction_fix
      @sub_direction = @direction
      @direction = 7
      # Face left if facing right, and face up if facing down
      @sub_direction = (@sub_direction == 6 ? 4 : @sub_direction == 2 ? 8 : @sub_direction)
    end
      return if pbLedge(-1,-1)
      return if pbEndSurf(-1,-1)
      return if moving?
    # When an up to left or a left to up course is passable
    if (passable?(@x, @y, 8) and passable?(@x, @y - 1, 4)) or
       (passable?(@x, @y, 4) and passable?(@x - 1, @y, 8))
      # Update coordinates
      @x -= 1
      @y -= 1
      # Increase steps
      increase_steps
    end
  end
  #--------------------------------------------------------------------------
  # * Move Upper Right
  #--------------------------------------------------------------------------
  def move_upper_right
    # If no direction fix
    unless @direction_fix
      @sub_direction = @direction
      @direction = 9
      # Face right if facing left, and face up if facing down
      @sub_direction = (@sub_direction == 4 ? 6 : @sub_direction == 2 ? 8 : @sub_direction)
    end
      return if pbLedge(1,-1)
      return if pbEndSurf(1,-1)
      return if moving?
    # When an up to right or a right to up course is passable
    if (passable?(@x, @y, 8) and passable?(@x, @y - 1, 6)) or
       (passable?(@x, @y, 6) and passable?(@x + 1, @y, 8))
      # Update coordinates
      @x += 1
      @y -= 1
      # Increase steps
      increase_steps
    end
  end
  #--------------------------------------------------------------------------
  # * Dash
  #--------------------------------------------------------------------------
  def dash_on
    if @dash_on != nil
      return @dash_on
    else
      return false
    end
  end
end