Rotate board puzzle

gistfile1.rb

require 'rubygems' # sudo gem install gosu --no-ri --no-rdoc
require 'gosu'

class Board < Array
    
  def rotate cw = false
    rotated = if cw
      transpose.map(&:reverse)
    else
      transpose.reverse
    end
    replace rotated.map(&:compact).map{|l| l.fill(nil, l.length..self.length-1)}
    flatten.compact.each{|s| s.to_angle = cw ? 90 : -90 }
  end
  
  def render
    each_with_index{|i, x| i.reverse.each_with_index{|s, y| s.render x, y if s }}
  end
  
end

class Stone < Gosu::Image
  attr_accessor :to_angle
    
  def initialize w, stone
    super w, stone, true
    @my_angle, @to_angle, @x, @y, @x_r, @y_r = 0, 0, 0, 0, 0, 0, 0
    @animation_speed, @center, @size = 0.3, 140, 64
  end
  
  def render x, y
    if (@to_angle - @my_angle).abs < @animation_speed
       @x_r +=  @animation_speed * (x-@x_r)
       @y_r +=  @animation_speed * (y-@y_r)
       @x, @y = @x_r, @y_r
       @my_angle = @to_angle = 0
    else
      @my_angle += @animation_speed * (@to_angle - @my_angle)
      f = @my_angle * (Math::PI/180.0)
      cos = Math.cos(f); sin = Math.sin(f)
      @x_r = ((@x - 2.0) * cos - (@y - 2.0) * sin) + 2.0
      @y_r = ((@y - 2.0) * cos + (@x - 2.0) * sin) + 2.0
    end
    
    draw_rot @x_r * @size + @center, @y_r * @size + @center, 0, 0
  end
end

class Game < Gosu::Window
  def initialize
    super 640, 480, false
    @board = Board.new.replace [[ Stone.new(self, "gem.png"), nil,  Stone.new(self, "gem.png"),  Stone.new(self, "gem.png"),Stone.new(self, "gem.png")],
      [ nil,  Stone.new(self, "gem.png"),  nil,  nil, Stone.new(self, "gem_blue.png")],
      [ nil,  nil,  Stone.new(self, "gem_blue.png"),  nil, nil],
      [ Stone.new(self, "gem_blue.png"),  nil,  Stone.new(self, "gem_blue.png"),  nil, nil],
      [ nil,  nil,  nil,  Stone.new(self, "gem_blue.png"), nil]
    ].transpose
  end
  
  def draw
    @board.render
  end
  
  def button_down key
    case key
    when Gosu::KbLeft then @board.rotate(true)
    when Gosu::KbRight then @board.rotate(false)
    end    
  end
  
end

Game.new.show