diff --git a/robotgame/level_bonus.py b/robotgame/level_bonus.py
index 128eec9..69b1f0a 100644
--- a/robotgame/level_bonus.py
+++ b/robotgame/level_bonus.py
@@ -30,6 +30,7 @@ import random
 import re
 import itertools
 
+import misc
 import level
 import player
 import tile
@@ -52,10 +53,8 @@ class Level(level.Level):
 
         self.draw_background()
 
-        emptys = list(itertools.product(range(2, 20), range(2, 20)))
-        for _ in range(150):
-            x, y = random.choice(emptys)
-            emptys.remove((x, y))
+        for x, y in misc.pick_random_elements(
+            list(itertools.product(range(2, 20), range(2, 20))), 150):
             self.objects.append(block.Block(self, 64 * x, 48 * y,
                                             self.imgs['block1'], movable=True))
 
diff --git a/robotgame/logic/lasermirror.py b/robotgame/logic/lasermirror.py
index 4cde2f7..169c264 100644
--- a/robotgame/logic/lasermirror.py
+++ b/robotgame/logic/lasermirror.py
@@ -33,6 +33,7 @@ import random
 import itertools
 from robotgame.logic.direction import *
 import robotgame.logic.rollingstone as rstone
+import robotgame.misc as misc
 
 class Mirror(object):
     pass
@@ -81,18 +82,16 @@ def generate_simple_playfield(nmirrors):
         succs = (lambda s: lambda d: succ(s(d)))(succs)
         source_direc = succ(source_direc)
 
-    emptys = set(itertools.product(range(12), range(12))) \
-        - set(playfield.keys())
-    emptys = set([(0, y) for y in range(12)]
-                 + [(11, y) for y in range(12)]
-                 + [(x, 0) for x in range(12)]
-                 + [(x, 11) for x in range(12)])
-    for _ in range(nlevers):
-        if not emptys:
-            raise Exception("Not enough space for all levers!")
-        pos = random.choice(list(emptys))
+    emptys = list(
+        set([(0, y) for y in range(12)]
+            + [(11, y) for y in range(12)]
+            + [(x, 0) for x in range(12)]
+            + [(x, 11) for x in range(12)])
+        - set(playfield.keys()))
+    if len(emptys) < nlevers:
+        raise Exception("Not enough space for all levers!")        
+    for pos in misc.pick_random_elements(emptys, nlevers):
         playfield[pos] = Lever
-        emptys.remove(pos)
     return playfield
 
 def _adjust(source_direc, w, h, x, y):
diff --git a/robotgame/logic/rollingstone.py b/robotgame/logic/rollingstone.py
index 8377402..75b5ca9 100644
--- a/robotgame/logic/rollingstone.py
+++ b/robotgame/logic/rollingstone.py
@@ -32,7 +32,9 @@ from __future__ import print_function
 import math
 import random
 import itertools
+
 from robotgame.logic.direction import *
+import robotgame.misc as misc
 
 class Blocker(object):
     pass
@@ -89,6 +91,9 @@ def generate_simple_playfield(width, height, nturns, nstones,
 
     'steps' is the number of steps used by the generated solution. It is not
     necessarily the lowest number of steps the playfield can be completed in.
+
+    This generator favours increasing the turn density the closer to the goal
+    it gets.
     """
 
     min_width, min_height = _min_play_size(nturns)
@@ -151,13 +156,10 @@ def generate_simple_playfield(width, height, nturns, nstones,
     del turns[-1]
     for p, d in turns:
         playfield[p] = d
-    emptys = set(itertools.product(range(width),
-                                   range(height))) - set(used_fields)
-    for _ in range(nstones):
-        if not emptys:
-            break
-        pos = random.choice(list(emptys))
-        emptys.remove(pos)
+
+    for pos in misc.pick_random_elements(
+        list(set(itertools.product(range(width), range(height)))
+             - set(used_fields)), nstones):
         playfield[pos] = Blocker
     return playfield, len(used_fields) - 1
 
diff --git a/robotgame/misc.py b/robotgame/misc.py
new file mode 100644
index 0000000..04547a3
--- /dev/null
+++ b/robotgame/misc.py
@@ -0,0 +1,9 @@
+from __future__ import print_function
+import random
+
+def pick_random_elements(xs, n):
+    for i in range(min(n, len(xs))):
+        i1 = random.randrange(i, len(xs))
+        yield xs[i1]
+        xs[i1] = xs[i]
+