diff --git a/Graphics/DrawingCombinators.hs b/Graphics/DrawingCombinators.hs
--- a/Graphics/DrawingCombinators.hs
+++ b/Graphics/DrawingCombinators.hs
@@ -30,7 +30,7 @@
     -- * Selection
     , selectRegion, click
     -- * Combinators
-    , over, empty
+    , over, overlay, empty
     -- * Initialization
     , init
     -- * Geometric Primitives
@@ -72,7 +72,7 @@
     DrawGL      :: DrawM () -> Draw ()
     TransformGL :: (forall x. DrawM x -> DrawM x) -> Draw a -> Draw a
     Empty       :: Draw a
-    Over        :: Draw a -> Draw a -> Draw a
+    Over        :: (a -> a -> a) -> Draw a -> Draw a -> Draw a
     FMap        :: (a -> b) -> Draw a -> Draw b
 
 -- |Draw a Drawing on the screen in the current OpenGL coordinate
@@ -85,7 +85,7 @@
     run' (DrawGL m) = m
     run' (TransformGL f m) = f (run' m)
     run' Empty = return ()
-    run' (Over a b) = run' b >> run' a
+    run' (Over f a b) = run' b >> run' a
     run' (FMap f d) = run' d
 
 -- |Like runDrawing, but clears the screen first.  This is so
@@ -103,7 +103,7 @@
 selectRegion ll ur drawing = do
     ((), recs) <- GL.getHitRecords 64 $ do -- XXX hard coded crap
         GL.preservingMatrix $ do
-            GLU.ortho2D (fst ll) (fst ur) (snd ll) (snd ur)
+            GLU.ortho2D (convReal $ fst ll) (convReal $ fst ur) (convReal $ snd ll) (convReal $ snd ur)
             runReaderT (draw' 0 drawing) initDrawCxt
             return ()
     let nameList = concatMap (\(GL.HitRecord _ _ ns) -> ns) (maybe [] id recs)
@@ -117,7 +117,7 @@
         return $! n+1
     draw' n (TransformGL f m) = f (draw' n m)
     draw' n Empty = return n
-    draw' n (Over a b) = do
+    draw' n (Over f a b) = do
         n' <- draw' n b
         draw' n' a
     draw' n (FMap f d) = draw' n d
@@ -128,14 +128,19 @@
         | otherwise            = (Nothing, n + 1)
     lookupName n names (TransformGL _ m) = lookupName n names m
     lookupName n names Empty = (Nothing, n)
-    lookupName n names (Over a b) =
+    lookupName n names (Over f a b) =
         let (lb, n')  = lookupName n  names b
             (la, n'') = lookupName n' names a
-        in (la `mplus` lb, n'')
+        in (joinMaybes f la lb, n'')
     lookupName n names (FMap f d) = 
         let (l, n') = lookupName n names d
         in (fmap f l, n')
 
+joinMaybes :: (a -> a -> a) -> Maybe a -> Maybe a -> Maybe a
+joinMaybes f Nothing x = x
+joinMaybes f x Nothing = x
+joinMaybes f (Just x) (Just y) = Just (f x y)
+
 click :: Vec2 -> Draw a -> IO (Maybe a)
 click (px,py) = selectRegion (px-e,py-e) (px+e,py+e)
     where
@@ -147,17 +152,20 @@
 initDrawCxt = DrawCxt { colorTrans = id }
 
 over :: Draw a -> Draw a -> Draw a
-over = Over
+over = overlay const
 
+overlay :: (a -> a -> a) -> Draw a -> Draw a -> Draw a
+overlay = Over
+
 empty :: Draw a
 empty = Empty
 
 instance Functor Draw where
     fmap = FMap
 
-instance Monoid (Draw a) where
+instance (Monoid a) => Monoid (Draw a) where
     mempty = empty
-    mappend = over
+    mappend = overlay mappend
 
 
 {----------------
@@ -173,6 +181,9 @@
         when (not success) $ fail "SDL_ttf initialization failed"
 
 
+convReal :: Double -> GL.GLdouble
+convReal = realToFrac
+
 {----------------
   Geometric Primitives
 -----------------}
@@ -181,23 +192,23 @@
 point :: Vec2 -> Draw ()
 point (ax,ay) = DrawGL $ lift $
     GL.renderPrimitive GL.Points $
-        GL.vertex $ GL.Vertex2 ax ay
+        GL.vertex $ GL.Vertex2 (convReal ax) (convReal ay)
 
 -- | Draw a line connecting the two given points.
 line :: Vec2 -> Vec2 -> Draw ()
 line (ax,ay) (bx,by) = DrawGL $ lift $ 
     GL.renderPrimitive GL.Lines $ do
-        GL.vertex $ GL.Vertex2 ax ay
-        GL.vertex $ GL.Vertex2 bx by
+        GL.vertex $ GL.Vertex2 (convReal ax) (convReal ay)
+        GL.vertex $ GL.Vertex2 (convReal bx) (convReal by)
 
 -- | Draw a regular polygon centered at the origin with n sides.
 regularPoly :: Int -> Draw ()
 regularPoly n = DrawGL $ lift $ do
     let scaler = 2 * pi / fromIntegral n :: Double
     GL.renderPrimitive GL.TriangleFan $ do
-        GL.vertex $ (GL.Vertex2 0 0 :: GL.Vertex2 Double)
+        GL.vertex $ (GL.Vertex2 0 0 :: GL.Vertex2 GL.GLdouble)
         forM_ [0..n] $ \s -> do
-            let theta = scaler * fromIntegral s
+            let theta = convReal (scaler * fromIntegral s)
             GL.vertex $ GL.Vertex2 (cos theta) (sin theta)
 
 -- | Draw a unit circle centered at the origin.  This is equivalent
@@ -210,7 +221,7 @@
 convexPoly points = DrawGL $ lift $ do
     GL.renderPrimitive GL.Polygon $ do
         forM_ points $ \(x,y) -> do
-            GL.vertex $ GL.Vertex2 x y
+            GL.vertex $ GL.Vertex2 (convReal x) (convReal y)
 
 {-----------------
   Transformations
@@ -221,7 +232,7 @@
 translate (byx,byy) = TransformGL $ \d -> do
     r <- ask
     lift $ GL.preservingMatrix $ do
-        GL.translate (GL.Vector3 byx byy 0)
+        GL.translate (GL.Vector3 (convReal byx) (convReal byy) 0)
         runReaderT d r
 
 -- | Rotate the given drawing counterclockwise by the
@@ -230,7 +241,7 @@
 rotate rad = TransformGL $ \d -> do
     r <- ask
     lift $ GL.preservingMatrix $ do
-        GL.rotate (180 * rad / pi) (GL.Vector3 0 0 1)
+        GL.rotate (180 * convReal rad / pi) (GL.Vector3 0 0 1)
         runReaderT d r
 
 -- | @scale x y d@ scales @d@ by a factor of @x@ in the
@@ -239,7 +250,7 @@
 scale x y = TransformGL $ \d -> do
     r <- ask
     lift $ GL.preservingMatrix $ do
-        GL.scale x y 1
+        GL.scale (convReal x) (convReal y) 1
         runReaderT d r
 
 {------------
@@ -265,7 +276,7 @@
     setColor oldcolor
     return result
     where
-    setColor (r,g,b,a) = lift $ GL.color $ GL.Color4 r g b a
+    setColor (r,g,b,a) = lift $ GL.color $ GL.Color4 (convReal r) (convReal g) (convReal b) (convReal a)
 
 -- | @color c d@ sets the color of the drawing to exactly @c@.
 color :: Color -> Draw a -> Draw a
@@ -389,9 +400,9 @@
     oldtex <- GL.get (GL.textureBinding GL.Texture2D)
     GL.textureBinding GL.Texture2D GL.$= (Just $ spriteObject spr)
     GL.renderPrimitive GL.Quads $ do
-        let (xofs, yofs) = (0.5 * spriteWidth spr, 0.5 * spriteHeight spr)
-            (xrat, yrat) = (spriteWidthRat spr, spriteHeightRat spr)
-        GL.texCoord $ GL.TexCoord2 0 (0 :: Double)
+        let (xofs, yofs) = (convReal $ 0.5 * spriteWidth spr, convReal $ 0.5 * spriteHeight spr)
+            (xrat, yrat) = (convReal $ spriteWidthRat spr, convReal $ spriteHeightRat spr)
+        GL.texCoord $ GL.TexCoord2 0 (0 :: GL.GLdouble)
         GL.vertex   $ GL.Vertex2 (-xofs) yofs
         GL.texCoord $ GL.TexCoord2 xrat 0
         GL.vertex   $ GL.Vertex2 xofs yofs
diff --git a/example.hs b/example.hs
--- a/example.hs
+++ b/example.hs
@@ -1,5 +1,6 @@
 import qualified Graphics.DrawingCombinators as Draw
 import qualified Graphics.UI.SDL as SDL
+import Data.Monoid
 
 resX = 640
 resY = 480
@@ -12,13 +13,17 @@
     return ()
 
 
-drawing :: Draw.Draw ()
-drawing = Draw.translate (0.0,0.2) 
+box :: Draw.Draw ()
+box = Draw.translate (0.0,0.2) 
         $ Draw.scale 0.3 0.3 
         $ Draw.color (1,0,0,0) 
         $ Draw.convexPoly
             [(1,1),(1,-1),(-1,-1),(-1,1)]
 
+drawing = fmap (const "A") (Draw.color (0,0,1,0) box)
+          `mappend`
+          fmap (const "B") (Draw.translate (-0.1,0.2) box)
+
 main :: IO ()
 main = do
     initScreen
@@ -39,7 +44,7 @@
                  hit <- Draw.click (x',y') drawing
                  case hit of
                       Nothing -> waitClicks
-                      Just () -> putStrLn "Hit!" >> waitClicks
+                      Just xs -> putStrLn xs >> waitClicks
              _ -> waitClicks
 
 untilM :: (Monad m) => (a -> Bool) -> m a -> m a
diff --git a/graphics-drawingcombinators.cabal b/graphics-drawingcombinators.cabal
--- a/graphics-drawingcombinators.cabal
+++ b/graphics-drawingcombinators.cabal
@@ -4,14 +4,14 @@
     have to go into the deep, dark world of imperative stateful
     programming just to draw stuff.  It supports 2D only (for now),
     with support drawing geometry, images, and text.
-Version: 0.2
+Version: 0.3
 Stability: experimental
 Synopsis: A functional interface to 2D drawing in OpenGL
-License: LGPL
+License: BSD3
 Category: Graphics
 Author: Luke Palmer
 Maintainer: lrpalmer@gmail.com
 Build-Type: Simple
-Build-Depends: base, mtl, containers, SDL, SDL-ttf, SDL-image, OpenGL
+Build-Depends: base <= 4, mtl, containers, SDL, SDL-ttf, SDL-image, OpenGL
 Exposed-Modules: Graphics.DrawingCombinators
 Extra-Source-Files: example.hs