diff -r 55b4c97d44c5 -r 5411a25cfca7 linetypes.py
--- a/linetypes.py	Sun Dec 10 15:37:26 2017 +0200
+++ b/linetypes.py	Sun Dec 10 15:45:50 2017 +0200
@@ -44,3 +44,14 @@
 
 class Quadrilateral(LineSegment):
     pass
+
+class Contour(LineSegment):
+    def __init__(self, *, color, geometry, control_points):
+        super().__init__(color = color, geometry = geometry)
+        self.control_points = control_points
+        assert(len(self.control_points) == 2)
+    def __repr__(self):
+        return str.format('linetypes.Contour(' \
+            'color = {color!r}, ' \
+            'geometry = {geometry!r}, ' \
+            'control_points = {control_points!r})', **self.__dict__)