diff --git a/processing_app/topics/lsystems/doily.rb b/processing_app/topics/lsystems/doily.rb
new file mode 100644
index 0000000..61b1731
--- /dev/null
+++ b/processing_app/topics/lsystems/doily.rb
@@ -0,0 +1,84 @@
+########################################################
+# A Doily fractal implemented using a
+# Lindenmayer System in JRubyArt by Martin Prout
+########################################################
+load_libraries :grammar
+
+# Doily class
+class Doily
+  include Processing::Proxy
+  attr_reader :draw_length, :vec, :theta, :axiom, :grammar
+  DELTA = 45 # degrees
+  def initialize(vec)
+    @axiom = 'F-F-F-F-F-F-F-F' # Axiom
+    rules =  { 'F' => 'F---F+F+F+F+F+F+F---F' }
+    @grammar = Grammar.new(axiom, rules)
+    @theta   = 0
+    @draw_length = 100
+    @vec = vec
+  end
+
+  def generate(gen)
+    @draw_length = draw_length * 0.4**gen
+    grammar.generate gen
+  end
+
+  def translate_rules(prod)
+    coss = ->(orig, alpha, len) { orig + len * DegLut.cos(alpha) }
+    sinn = ->(orig, alpha, len) { orig - len * DegLut.sin(alpha) }
+    [].tap do |pts| # An array to store line vertices as Vec2D
+      prod.each do |ch|
+        case ch
+        when 'F'
+          pts << vec.copy
+          @vec = Vec2D.new(
+            coss.call(vec.x, theta, draw_length),
+            sinn.call(vec.y, theta, draw_length)
+          )
+          pts << vec
+        when '+'
+          @theta += DELTA
+        when '-'
+          @theta -= DELTA
+        else
+          puts("character #{ch} not in grammar")
+        end
+      end
+    end
+  end
+end
+
+attr_reader :points
+
+def setup
+  sketch_title 'Doily'
+  doily = Doily.new(Vec2D.new(width * 0.35, height * 0.2))
+  production = doily.generate 4 # 4 generations looks OK
+  @points = doily.translate_rules(production)
+  no_loop
+end
+
+def draw
+  background(0)
+  render points
+end
+
+def render(points)
+  no_fill
+  stroke 200.0
+  stroke_weight 3
+  begin_shape
+  points.each_slice(2) do |v0, v1|
+    v0.to_vertex(renderer)
+    v1.to_vertex(renderer)
+  end
+  end_shape
+end
+
+def renderer
+  @renderer ||= AppRender.new(self)
+end
+
+def settings
+  size(800, 800)
+end