再帰曲線（ゴシック・フリーズ）描画のアニメーション版

turtle_sample3a.rb

require 'oekaki'

Oekaki.app width: 420, height: 420, title: "Turtle" do
  draw {clear}
    
  t = Oekaki::Turtle.new
  t.color(0xffff, 0x45ff, 0)    #orangered
  t.move(-200, -200)
  t.left(45)
  
  e = Enumerator.new do |y|
    drawing = lambda do |n, l|
      if n == 1
        y << [t, l]
      else
        drawing[n - 1, l / 3]
        t.left(90) 
        drawing[n - 1, l / 3] 
        t.right(90)
        drawing[n - 1, l / 3] 
        t.right(90)
        drawing[n - 1, l / 3] 
        t.left(90)
        drawing[n - 1, l / 3] 
      end
    end
    drawing[4, 400 * sqrt(2)]
  end
  
  timer(100) do
    t, l = e.next rescue next
    t.forward(l)
  end
end