RMVXAce Slopes and Stairs

# I did not make this script, a user named "Shaz" did, on this
# thread: http://forums.rpgmakerweb.com/index.php?/topic/9139-simple-slopes/
# I made trivial modifications, and fixed an issue where characters
# would sometimes face in weird directions when moving on stairs.

# terrain tag for stairs sloping from the bottom-left to upper-right
SLOPE_UP_TAG = 4

# terrain for stairs sloping from the top-left to bottom-right
SLOPE_DOWN_TAG = 6 

class Game_CharacterBase

  alias original_move_straight move_straight

  def diagonal_override(d)
    this_override = $game_map.terrain_tag(@x, @y)
    new_x = $game_map.round_x_with_direction(@x, d)
    new_y = $game_map.round_y_with_direction(@y, d)
    new_override = $game_map.terrain_tag(new_x, new_y)

    if(new_override == SLOPE_UP_TAG && d == 6)
      return 6, 8
    elsif(new_override == SLOPE_DOWN_TAG && d == 4)
      return 4, 8
    elsif(this_override == SLOPE_UP_TAG && (d == 4 || d == 2))
      return 4, 2
    elsif(this_override == SLOPE_DOWN_TAG && (d == 6 || d == 2))
      return 6, 2
    else
      return 0, 0
    end
  end

  def move_straight(d, turn_ok = true)
    x_direction, y_direction = diagonal_override(d)
    if x_direction != 0 && y_direction != 0
      set_direction(x_direction)
      move_diagonal(x_direction, y_direction)
    else
      original_move_straight(d, turn_ok)
    end
  end
end