diff --git a/robotgame/logic/colourboxes.py b/robotgame/logic/colourboxes.py
new file mode 100644
index 0000000..e4d1fd7
--- /dev/null
+++ b/robotgame/logic/colourboxes.py
@@ -0,0 +1,87 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# This file is part of ROBOTGAME
+#
+# ROBOTGAME is free software: you can redistribute it and/or modify it under the
+# terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+#
+# ROBOTGAME is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# ROBOTGAME.  If not, see <http://www.gnu.org/licenses/>.
+#
+# ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
+#
+#                         colourboxes.py
+#                     --------------------
+#       date created : Wed Aug 8 2012
+#          copyright : (C) 2012 Niels G. W. Serup
+#      maintained by : Niels G. W. Serup <ns@metanohi.name>
+
+import random
+
+def generate_colour_boxes(nwells, nboxes):
+    """
+    Generate colour boxes that can be used to make all wells white.
+
+    Arguments:
+    nwells -- number of wells
+    nboxes -- maximum number of boxes needed to make all wells white.
+
+    Return [[(r, g, b)]]
+      where r : 0|1,  g : 0|1,  b : 0|1
+    """
+    
+    nbits = nwells * 3
+    data = [[0 for _ in range(nboxes)] for _ in range(nbits)]
+
+    def insert_1():
+        t = random.randrange(0, nboxes)
+        for y in range(t, nboxes) + range(0, t):
+            if data[x][y] == 0:
+                data[x][y] = 1
+                break
+
+    for x in range(len(data)):
+        insert_1()
+        for _ in range(random.randrange(0, (nboxes + 1) / 2)):
+            insert_1()
+            insert_1()
+
+    boxes = []
+    for y in range(nboxes):
+        box = []
+        boxes.append(box)
+        for x in range(0, nbits, 3):
+            r = data[x][y]
+            g = data[x + 1][y]
+            b = data[x + 2][y]
+            box.append((r, g, b))
+    return boxes
+
+def generate_random_box(nwells):
+    r = lambda: random.choice((0, 1))
+    return [(r(), r(), r()) for _ in range(nwells)]
+
+def makes_all_wells_white(boxes):
+    """
+    Determine if the boxes make all wells white when XOR'ed together.
+    """
+    
+    total = 0
+    for box in boxes:
+        n = 0
+        for r, g, b in box:
+            n <<= 1
+            n |= r
+            n <<= 1
+            n |= g
+            n <<= 1
+            n |= b
+        total ^= n
+    return total == 2**(len(boxes[0]) * 3) - 1
diff --git a/robotgame/logic/rollingstone.py b/robotgame/logic/rollingstone.py
index 35f2859..77d119e 100644
--- a/robotgame/logic/rollingstone.py
+++ b/robotgame/logic/rollingstone.py
@@ -129,7 +129,7 @@ def generate_simple_playfield(width, height, nturns, nstones):
             turns.append(((x1, y1), None))
             x, y = x1, y1
     turns.append(((width - 1, height - 1), None))
-    
+
     if do_transpose:
         turns[:] = [((y, x), {
                     Down:  Right,
diff --git a/tests/colourboxes_tests.py b/tests/colourboxes_tests.py
new file mode 100644
index 0000000..48bcbca
--- /dev/null
+++ b/tests/colourboxes_tests.py
@@ -0,0 +1,17 @@
+
+from __future__ import print_function
+import unittest
+from robotgame.logic.colourboxes import *
+
+
+class ColourboxesTest(unittest.TestCase):
+    def test_generation(self):
+        for args in ((1, 1),
+                     (2, 2),
+                     (3, 3)):
+            boxes = generate_colour_boxes(*args)
+            print(boxes)
+            self.assertTrue(makes_all_wells_white(boxes))
+
+if __name__ == '__main__':
+    unittest.main()