Ruby Processing Context Free DSL sketch with custom primitive

isoceles.rb

load_library 'context_free'

def setup_the_spiral
  @spiral= ContextFree.define do
    ############ Begin defining custom terminal, an isoceles triangle	  
    class << self     
      define_method(:isoceles) do |some_options| # isoceles triangle
        size, options = *self.get_shape_values(some_options)
        rot = options[:rotation]
        @app.rotate(rot) if rot 
        @app.triangle(-0.5 * size, -0.5 * size, -0.5 * size, 0.5 * size, 0.5 * size, 0.5 * size)
        @app.rotate(-rot) if rot
      end 
    end
    ########### End definition of custom terminal 'isoceles'
    rule :spiral do
      isoceles :brightness => -1, :rotation => 90
      spiral :rotation => 135, :size => 1/sqrt(2), :x => 1/sqrt(2)
    end
  end
end

def setup
  size 600, 400
  background 255
  smooth
  setup_the_spiral
  draw_it
end

def draw_it
  @spiral.render :spiral, :start_x => width/3, :start_y => height/2, 
               :size => height
end