diff --git a/prototype/circles.py b/prototype/circles.py
index 84be1b8..f4cbffb 100644
--- a/prototype/circles.py
+++ b/prototype/circles.py
@@ -5,7 +5,7 @@ import operator
 
 # scale in inkscape
 # 1 unit = 0.283 mm
-scale = 1000.0/282.222
+svg_scale = 1000.0/282.222
 
 def svg_circle(id, name, c, r):
     # create circle object in svg notation
@@ -48,12 +48,12 @@ def svg_puzzle(p, size, angle):
     p4 = p - size * v1
 
     # convert to svg units
-    p1 *= scale
-    p2 *= scale
-    p3 *= scale
-    p4 *= scale
+    p1 *= svg_scale
+    p2 *= svg_scale
+    p3 *= svg_scale
+    p4 *= svg_scale
 
-    radius_scaled = 1.25 * size * scale
+    radius_scaled = 1.25 * size * svg_scale
 
     text = ['      <path \n     '
             '        id="path666" \n       '
@@ -63,6 +63,58 @@ def svg_puzzle(p, size, angle):
 
     return text
 
+def svg_line_puzzle(start, end, puzzle_scale=1.0, linewidth=0.50):
+    v = end - start
+    dist = np.linalg.norm(v)
+    size = dist / 10.0 * puzzle_scale
+    v = v / dist
+    angle = math.atan2(v[1], v[0])
+
+    p = np.mean([start, end], axis=0)
+
+    # compute points
+    """
+        v1 and v2 are orthogonal vectors
+
+        construction of points (starting at p):
+
+           p3 <------   -2 v1  ------ p2
+                                      ^
+                                      |
+                                      v2
+                                      |
+                                      |
+           p4 <-- -v1 --  p -- v1 --> p1
+
+        then between points p2 and p3 with draw an arc
+    """
+
+    v1 = np.array([np.cos(angle), np.sin(angle)])
+    v2 = np.array([v1[1], -v1[0]])
+    p1 = p - size * v1
+    p2 = p1 + size * v2
+    p3 = p2 + 2.0 * size * v1
+    p4 = p + size * v1
+
+    # convert to svg units
+    p1 *= svg_scale
+    p2 *= svg_scale
+    p3 *= svg_scale
+    p4 *= svg_scale
+    start *= svg_scale
+    end *= svg_scale
+
+    radius_scaled = 1.25 * size * svg_scale
+
+    text = ['      <path \n     '
+            '        id="path666" \n       '
+            '        style="fill:none;stroke:#000000;stroke-width:{}mm" \n'
+            '        d="M {} {} L {} {} L {} {} A {} {} 0 1 1 {} {} L {} {} L {} {}"'
+            '      />\n'.format(linewidth, start[0], start[1], p1[0], p1[1], p2[0], p2[1], radius_scaled, radius_scaled,
+                                p3[0], p3[1], p4[0], p4[1], end[0], end[1])]
+
+    return text
+
 def svg_half_circle(id, name, c, r, angle, orientation_flag=1):
     # draws half a circle centered at c with radius r
     # angle specifies how the half circle should be rotated
@@ -74,13 +126,13 @@ def svg_half_circle(id, name, c, r, angle, orientation_flag=1):
     # compute starting point
     v = np.array([np.cos(angle), np.sin(angle)])
     begin = c + r * v   # in millimeters
-    begin *= scale      # in svg units
+    begin *= svg_scale      # in svg units
 
     # compute end point
     end = c - r * v     # in millimeters
-    end *= scale        # in svg units
+    end *= svg_scale        # in svg units
 
-    radius_scaled = r * scale   # radius in svg units
+    radius_scaled = r * svg_scale   # radius in svg units
 
     text = ['      <path \n     '
             '        id="path666" \n       '
@@ -92,9 +144,9 @@ def svg_half_circle(id, name, c, r, angle, orientation_flag=1):
     return text
 
 def svg_arc(p1, p2, r,  large_arc, sweep):
-    begin = p1 * scale
-    end = p2 * scale
-    radius_scaled = r * scale
+    begin = p1 * svg_scale
+    end = p2 * svg_scale
+    radius_scaled = r * svg_scale
     text = ['      <path \n     '
             '        id="path666" \n       '
             '        style="fill:none;stroke:#ff0000;stroke-width:0.60000002" \n'
@@ -613,14 +665,16 @@ class PlateLayout:
         vunit = np.array([np.cos(a), np.sin(a)])
         p1 = vunit * self.target_center_hole_radius
         p2 = vunit * r1
-        text = svg_line(p1, p2, 0.1)
+        #text = svg_line(p1, p2, 0.1)
+        text = svg_line_puzzle(p1, p2)
         f_lines = f_lines + text
 
         r2 = np.linalg.norm(np.array(self.tube_1_coords[k])) + self.target_radius_1
         p3 = vunit * r2
         r3 = self.target_plate_radius - self.plate_module
         p4 = vunit * r3
-        text = svg_line(p3, p4, 0.1)
+        text = svg_line_puzzle(p3, p4)
+        #text = svg_line(p3, p4, 0.1)
         f_lines = f_lines + text
 
         outer_point_1 = p4
@@ -632,14 +686,16 @@ class PlateLayout:
         vunit = np.array([np.cos(a), np.sin(a)])
         p1 = vunit * self.target_center_hole_radius
         p2 = vunit * r1
-        text = svg_line(p1, p2, 0.1)
+        #text = svg_line(p1, p2, 0.1)
+        text = svg_line_puzzle(p1, p2)
         f_lines = f_lines + text
 
         r2 = np.linalg.norm(np.array(self.tube_1_coords[k_next])) + self.target_radius_1
         p3 = vunit * r2
         r3 = self.target_plate_radius - self.plate_module
         p4 = vunit * r3
-        text = svg_line(p3, p4, 0.1)
+        #text = svg_line(p3, p4, 0.1)
+        text = svg_line_puzzle(p3, p4)
         f_lines = f_lines + text
 
         outer_point_2 = p4
@@ -663,8 +719,8 @@ class PlateLayout:
                     coordinates.append(c_running)
                     pass
 
-                dist_1 = [np.linalg.norm(c - outer_point_1*scale) for c in coordinates]
-                dist_2 = [np.linalg.norm(c - outer_point_2 * scale) for c in coordinates]
+                dist_1 = [np.linalg.norm(c - outer_point_1 * svg_scale) for c in coordinates]
+                dist_2 = [np.linalg.norm(c - outer_point_2 * svg_scale) for c in coordinates]
 
                 # find minimum distance and keep only points between the two distances
                 # problem: does not consider manual rotation of the plate
@@ -674,11 +730,6 @@ class PlateLayout:
                 pass
                 #f_lines[k] = gear_data[0:index+1] + gear_data[-2:]
 
-        c = self.tube_1_coords[k]
-        angle = self.tube_1_angles[k]
-        text = svg_puzzle(c, 4, angle)
-        f_lines = f_lines + text
-
         return f_lines
 
     def output_whole(self, f_lines):