diff --git a/CHANGES b/CHANGES
--- a/CHANGES
+++ b/CHANGES
@@ -1,4 +1,80 @@
 
+
+0.36.0 to 0.37.0:
+
+  * The bounding box constructors have been renamed - @bbox@ is 
+    now @boundingBox@ and @obbox@ becomes @oboundingBox@. The 
+    rationale for this change is that the names very cryptic in 
+    the first place and the constructors are used infrequently 
+    when @bbox@ in particular makes a descriptive variable name.
+
+  * Changes to the Picture and Primitive types to enable better
+    concatenation which is used heavily by Wumpus-Basic. The 
+    Picture API exposes a new function @primCat@.
+
+  * SVG /font delta context/ change - font deltas are now 
+    annotated on Primitives not Pictures. The type of the 
+    function @fontDeltaContext@ in @Core.Picture@ has changed 
+    accordingly.
+
+  * SVG hyperlink change - hyperlinks no longer group primitives
+    (although a group of primitives can be hyperlinked). The 
+    function @xlinkGroup@ has been removed from @Core.Picture@, 
+    it is replaced by @xlink@.
+
+  * @Core.Picture@ - the argument order for the function 
+    @rtextlabel@ has been changed, the positions of the angle and 
+    bottom-left corner have been swapped.
+
+0.35.0 to 0.36.0:
+
+  * API / behaviour change - rotation on primitives changed. New 
+    functions have been added to create rotated text labels and 
+    ellipses (@rtextlabel@, @rstrokeEllipse@, etc.), and 
+    Primitives have been made instances of the Affine classes
+    except for the general matrix Transform class. The old
+    functions for transforming Primitives (@rotatePrim@, 
+    @scalePrim@, etc.) have been removed. The demos (Rotated.hs,
+    Scaled.hs, Translated.hs) have been removed as they pertain 
+    to the old behaviour, there are new demos highlighting the
+    new behaviour (TransformEllipse.hs, etc.).
+
+  * Major change - removed the PrimElement type. The (opaque) 
+    Primitive type has been changed to incorporate a grouping 
+    constructor equivalent to PrimElement\'s @XLinkGroup@ 
+    contructor. The change has made the implementation of SVG 
+    hyperlinks more efficient, but has forced various type 
+    signatures to change in @Core.Picture@. Client code will 
+    also have to change type signatures - @PrimElement@ becomes
+    @Primitive@.
+
+  * @Core.PtSize@ - the class @FromPtSize@ has been given a @Num@
+    superclass constraint. This can shorten type signatures of 
+    functions that use @fromPtSize@.
+
+  * Corrected a bug where textlabels would generate an invalid
+    bounding box and cause a runtime error when supplied with an
+    empty string. Now there is no runtime error - and /no-ops/ 
+    are generated in the output.
+
+  * Internal changes - moved @PrimCTM@ from @Core.PictureInternal@
+    into separate module. Moved /utility/ modules into their own 
+    directory @Utils@. Move /text/ modules into their own 
+    directory @Text@. 
+
+  * Removed dependency on @algebra@ for @Semigroup@. The 
+    equivalent @append@ operation on @BoundingBox@ is 
+    @boundaryUnion@.
+
+  * Renamed the @Core.GraphicsState@ to @Core.GraphicProps@. 
+    Moved the property datatypes from @Core.PictureInternal@ into 
+    @Core.GraphicProps@ (StrokeProps, LabelProps, etc.).
+
+  * Moved @wumpus_default_font@ from @Core.Picture@ into 
+    @Core.Graphic.Props@.
+
+  * Haddock docs improved.
+
 0.34.0 to 0.35.0:
 
   * Bug fix - PostScript output - when more than one stroke 
diff --git a/demo/DeltaPic.hs b/demo/DeltaPic.hs
--- a/demo/DeltaPic.hs
+++ b/demo/DeltaPic.hs
@@ -1,6 +1,9 @@
 {-# LANGUAGE TypeFamilies               #-}
 {-# OPTIONS -Wall #-}
 
+-- SVG ouptut has some ability to minimization font change code.
+-- This example demonstrates it.
+
 module DeltaPic where
 
 import Wumpus.Core
@@ -25,14 +28,14 @@
 
 
 pic1 :: DPicture
-pic1 = fontDeltaContext delta_ctx $ frame 
+pic1 = frame1 $ fontDeltaContext delta_ctx $ primGroup  
           [ helveticaLabel 18 "Optimized - size and face"  (P2 0 60)
           , helveticaLabel 14 "Optimized - face only"      (P2 0 40)
           , courierLabel      "No optimization"            (P2 0 20)
           ]
   where
    delta_ctx  = FontAttr 18 common_ff
- 
+   frame1 a   = frame [a] 
 
 common_ff :: FontFace
 common_ff = FontFace "Helvetica" "Helvetica" SVG_REGULAR latin1_font_encoder
diff --git a/doc-src/Guide.lhs b/doc-src/Guide.lhs
--- a/doc-src/Guide.lhs
+++ b/doc-src/Guide.lhs
@@ -23,7 +23,7 @@
 \section{About \wumpuscore}
 %-----------------------------------------------------------------
 
-This guide was last updated for \wumpuscore version 0.36.0.
+This guide was last updated for \wumpuscore version 0.37.0.
 
 \wumpuscore is a Haskell library for generating 2D vector 
 pictures. It was written with portability as a priority, so it has 
@@ -124,14 +124,15 @@
 type to represent them.
 
 \item[\texttt{Wumpus.Core.TextEncoder.}]
-Types for handling extended character codes e.g. for accented 
-characters or the Symbol font. Special characters generally have 
-to be escaped in the PostScript and SVG output, this module 
-provides data types for lookup tables between the escaped 
-character code and its PostScript or SVG representation. 
+Types for handling extended character codes within fonts e.g. 
+for accented characters or the Symbol font. Special characters 
+generally have to be escaped in the PostScript and SVG output, 
+this module provides data types for lookup tables between the 
+escaped character code and its PostScript or SVG representation. 
 Text encoders are associated with fonts - glyphs within a font 
 are located by their character name / code. Currently 
-\wumpuscore has encoders for Latin1 and the Symbol font. 
+\wumpuscore has encoders for the Standard Latin Encoding table 
+and the Symbol font character set. 
 
 \item[\texttt{Wumpus.Core.TextLatin1.}]
 A instance of the TextEncoder type for mapping Latin 1 characters
@@ -315,6 +316,9 @@
 \texttt{Wumpus.Basic.SafeFonts} encoding the fonts in this list 
 and matching them to their appropriate \texttt{TextEncoder}.
 
+Note that the Symbol font, whilst incredibly useful, is a taboo
+with the W3C and they do not condone its use in SVG or HTML.
+Likewise, certain browsers reject it out of course.
 
 \begin{tabular}{ l l }
 PostScript name   & SVG name      \\
@@ -331,7 +335,7 @@
 Courier-Oblique   & Courier New - style="italic" \\
 Courier-Bold      & Courier New - font-weight="bold" \\
 Courier-Bold-Oblique & Courier New - style="italic", font-weight="bold" \\
-Symbol & Symbol \\
+Symbol & (Symbol - see text) \\
 \hline
 \end{tabular}
 
diff --git a/doc/Guide.pdf b/doc/Guide.pdf
Binary files a/doc/Guide.pdf and b/doc/Guide.pdf differ
diff --git a/src/Wumpus/Core/AffineTrans.hs b/src/Wumpus/Core/AffineTrans.hs
--- a/src/Wumpus/Core/AffineTrans.hs
+++ b/src/Wumpus/Core/AffineTrans.hs
@@ -150,7 +150,7 @@
 -- | Type class for translation.
 --
 class Translate t where
-  translate :: DUnit t -> DUnit t -> t -> t
+  translate :: u ~ DUnit t => u -> u -> t -> t
 
 instance Num u => Translate (Point2 u) where
   translate dx dy (P2 x y) = P2 (x+dx) (y+dy)
diff --git a/src/Wumpus/Core/BoundingBox.hs b/src/Wumpus/Core/BoundingBox.hs
--- a/src/Wumpus/Core/BoundingBox.hs
+++ b/src/Wumpus/Core/BoundingBox.hs
@@ -31,9 +31,11 @@
   -- * Type class
   , Boundary(..)
   
+  -- * Constructors
+  , boundingBox
+  , oboundingBox
+  
   -- * Operations
-  , bbox
-  , obbox
   , destBoundingBox
   , boundaryUnion 
   , traceBoundary
@@ -124,27 +126,32 @@
 
 --------------------------------------------------------------------------------
 
--- | 'bbox' : @lower_left_corner * upper_right_corner -> BoundingBox@
+-- | 'boundingBox' : @lower_left_corner * upper_right_corner -> BoundingBox@
 --
 -- Contruct a bounding box, vis the BBox constructor with range 
 -- checking on the corner points.
 --
--- @bbox@ throws an error if the width or height of the 
+-- 'boundingBox' throws an error if the width or height of the 
 -- constructed bounding box is negative.
 --
-bbox :: Ord u => Point2 u -> Point2 u -> BoundingBox u
-bbox ll@(P2 x0 y0) ur@(P2 x1 y1) 
-   | x0 <= x1 && y0 <= y1 = BBox ll ur 
-   | otherwise            = error "Wumpus.Core.BoundingBox.bbox - malformed."
+boundingBox :: Ord u => Point2 u -> Point2 u -> BoundingBox u
+boundingBox ll@(P2 x0 y0) ur@(P2 x1 y1) 
+    | x0 <= x1 && y0 <= y1 = BBox ll ur 
+    | otherwise            = error "Wumpus.Core.boundingBox - malformed."
 
 
--- | 'obbox' : @width * height -> BoundingBox@
+-- | 'oboundingBbox' : @width * height -> BoundingBox@
 --
 -- Create a BoundingBox with bottom left corner at the origin,
 -- and dimensions @w@ and @h@.
 --
-obbox :: Num u => u -> u -> BoundingBox u
-obbox w h = BBox zeroPt (P2 w h)
+-- 'oboundingBox' throws an error if either the suppplied width 
+-- or height is negative.
+-- 
+oboundingBox :: (Num u, Ord u) => u -> u -> BoundingBox u
+oboundingBox w h 
+    | h >= 0 && w >= 0 = BBox zeroPt (P2 w h)
+    | otherwise        = error "Wumpus.Core.oboundingBox - malformed."
 
 -- | 'destBoundingBox' : @ bbox -> (lower_left_x, lower_lefy_y, 
 --      upper_right_x, upper_right_y)@
diff --git a/src/Wumpus/Core/FontSize.hs b/src/Wumpus/Core/FontSize.hs
--- a/src/Wumpus/Core/FontSize.hs
+++ b/src/Wumpus/Core/FontSize.hs
@@ -247,7 +247,7 @@
 
 textBoundsBody :: (Num u, Ord u, FromPtSize u) 
                => FontSize -> Point2 u -> Int -> BoundingBox u
-textBoundsBody sz baseline_left len = bbox bl tr 
+textBoundsBody sz baseline_left len = boundingBox bl tr 
   where
     h           = fromPtSize $ textHeight sz
     w           = fromPtSize $ textWidth  sz len
diff --git a/src/Wumpus/Core/OutputPostScript.hs b/src/Wumpus/Core/OutputPostScript.hs
--- a/src/Wumpus/Core/OutputPostScript.hs
+++ b/src/Wumpus/Core/OutputPostScript.hs
@@ -38,7 +38,7 @@
 import Wumpus.Core.Text.TextInternal
 import Wumpus.Core.TrafoInternal
 import Wumpus.Core.Utils.Common
-import Wumpus.Core.Utils.OneList
+import Wumpus.Core.Utils.JoinList
 import Wumpus.Core.Utils.FormatCombinators
 
 
@@ -279,14 +279,13 @@
 picture :: (Real u, Floating u, PSUnit u) => Picture u -> PsMonad Doc
 picture (Leaf    (_,xs) ones)   = bracketTrafos xs $ oneConcat primitive ones
 picture (Picture (_,xs) ones)   = bracketTrafos xs $ oneConcat picture ones
-picture (Group   (_,xs) _ pic) = bracketTrafos xs (picture pic)
 picture (Clip    (_,xs) cp pic) = bracketTrafos xs $
     (\d1 d2 -> vcat [ps_gsave,d1,d2,ps_grestore])
       <$> clipPath cp <*> picture pic <* resetGS
 
 
 
-oneConcat :: (a -> PsMonad Doc) -> OneList a -> PsMonad Doc
+oneConcat :: (a -> PsMonad Doc) -> JoinList a -> PsMonad Doc
 oneConcat fn ones = outstep (viewl ones)
   where
     outstep (e :< rest)   = fn e >>= \a -> instep a (viewl rest)
@@ -296,14 +295,17 @@
     instep ac (e :< rest) = fn e >>= \a -> instep (ac `vconcat` a) (viewl rest)
 
 
--- No action is taken for hyperlinks in PostScript.
+-- No action is taken for hyperlinks or font context changes in 
+-- PostScript.
 --
 
 primitive :: (Real u, Floating u, PSUnit u) => Primitive u -> PsMonad Doc
 primitive (PPath props pp)     = primPath props pp
 primitive (PLabel props lbl)   = primLabel props lbl
 primitive (PEllipse props ell) = primEllipse props ell
-primitive (PGroup _ ones)      = oneConcat primitive ones
+primitive (PContext _ chi)     = primitive chi
+primitive (PLink _ chi)        = primitive chi
+primitive (PGroup ones)        = oneConcat primitive ones
 
 
 primPath :: PSUnit u
diff --git a/src/Wumpus/Core/OutputSVG.hs b/src/Wumpus/Core/OutputSVG.hs
--- a/src/Wumpus/Core/OutputSVG.hs
+++ b/src/Wumpus/Core/OutputSVG.hs
@@ -49,7 +49,7 @@
 import Wumpus.Core.TrafoInternal
 import Wumpus.Core.Utils.Common
 import Wumpus.Core.Utils.FormatCombinators
-import Wumpus.Core.Utils.OneList
+import Wumpus.Core.Utils.JoinList
 
 import Control.Applicative hiding ( empty, some )
 import Data.Maybe
@@ -106,7 +106,7 @@
 askGraphicsState = SvgMonad $ \_ r2 s -> (r2,s)
 
 asksGraphicsState :: (GraphicsState -> a) -> SvgMonad a
-asksGraphicsState fn = SvgMonad $ \_ r2 s -> (fn r2,s)
+asksGraphicsState fn = fmap fn askGraphicsState
 
 askFontAttr :: SvgMonad FontAttr
 askFontAttr = asksGraphicsState $ \r -> 
@@ -189,12 +189,11 @@
                           ; d2  <- picture pic
                           ; return (vconcat d1 (elem_g (attr_clip_path lbl) d2))
                           } 
-picture (Group   (_,xs) fn pic) = bracketTrafos xs $ bracketGS fn (picture pic)
 
 
 
 
-oneConcat :: (a -> SvgMonad Doc) -> OneList a -> SvgMonad Doc
+oneConcat :: (a -> SvgMonad Doc) -> JoinList a -> SvgMonad Doc
 oneConcat fn ones = outstep (viewl ones)
   where
     outstep (e :< rest)   = fn e >>= \a -> instep a (viewl rest)
@@ -205,13 +204,12 @@
 
 
 primitive :: (Real u, Floating u, PSUnit u) => Primitive u -> SvgMonad Doc
-primitive (PPath props pp)     = primPath props pp
-primitive (PLabel props lbl)   = primLabel props lbl
-primitive (PEllipse props ell) = primEllipse props ell
-primitive (PGroup mb ones)     = 
-    case mb of
-      Nothing -> oneConcat primitive ones
-      Just xl -> drawXLink xl <$> oneConcat primitive ones
+primitive (PPath props pp)      = primPath props pp
+primitive (PLabel props lbl)    = primLabel props lbl
+primitive (PEllipse props ell)  = primEllipse props ell
+primitive (PContext fa chi)     = bracketGS fa (primitive chi)
+primitive (PLink hypl chi)      = drawXLink hypl <$> primitive chi
+primitive (PGroup ones)         = oneConcat primitive ones
  
 
 drawXLink :: XLink -> Doc -> Doc
@@ -405,11 +403,27 @@
     attr_stroke_dashoffset n <+> attr_stroke_dasharray xs
 
 
+data FontMatch = FullMatch | DeltaPtSize | DeltaFont
+  deriving (Eq,Show,Ord) 
 
+
 deltaFontAttrs :: FontAttr -> SvgMonad Doc
-deltaFontAttrs fa = 
-    (\inh -> if fa == inh then empty else makeFontAttrs fa) <$> askFontAttr
+deltaFontAttrs fa = (\inh -> step $ fontMatch inh fa) <$> askFontAttr
+  where
+    step FullMatch      = empty
+    step DeltaPtSize    = attr_font_size $ font_size fa
+    step DeltaFont      = makeFontAttrs fa
 
+
+fontMatch :: FontAttr -> FontAttr -> FontMatch
+fontMatch (FontAttr s1 f1) (FontAttr s2 f2) 
+   | s1 == s2 && f1 == f2 = FullMatch
+   | f1 == f2             = DeltaPtSize
+   | otherwise            = DeltaFont
+
+-- Note this is always adding FontSize - there are cases where 
+-- this is redundant. 
+--
 makeFontAttrs :: FontAttr -> Doc
 makeFontAttrs (FontAttr sz face) = 
     attr_font_family (svg_font_family face) <+> attr_font_size sz 
@@ -430,27 +444,23 @@
         space <> attr_font_weight "bold" <+> attr_font_style "oblique"
 
 
--- NOTE - as is only practical to delta the FontFace attributes 
--- it might be good to specialize / simplify the graphics state
--- GSUpdate to a simpler type rather than a functional one...
 
+-- Always update both the size and font-family even if only one
+-- changes.
+--
+-- This seems more in the spirit of a font delta operation.
+--
 bracketGS :: FontCtx -> SvgMonad Doc -> SvgMonad Doc
 bracketGS (FontCtx new_font) mf = 
-    (\old body -> mkElem old body) 
-        <$> askGraphicsState <*> runLocalGS updateF mf
+    (\old body -> mkElem (old == new_font) body) 
+        <$> askFontAttr <*> runLocalGS updateF mf
   where
-    mkElem old body 
-      | fontMatch old new_font = elem_g_no_attrs body
-      | otherwise              = let a = makeFontAttrs new_font
-                                 in elem_g a body
+    mkElem True body = elem_g_no_attrs body
+    mkElem _    body = let a = makeFontAttrs new_font in elem_g a body
 
     updateF s = s { gs_font_size = font_size new_font
                   , gs_font_face = font_face new_font }
                 
-
-fontMatch :: GraphicsState -> FontAttr -> Bool
-fontMatch gs fa = 
-   gs_font_size gs == font_size fa && gs_font_face gs == font_face fa
 
 
 --------------------------------------------------------------------------------
diff --git a/src/Wumpus/Core/PageTranslation.hs b/src/Wumpus/Core/PageTranslation.hs
--- a/src/Wumpus/Core/PageTranslation.hs
+++ b/src/Wumpus/Core/PageTranslation.hs
@@ -47,13 +47,14 @@
 trivPic (Leaf lc ones)      = Leaf lc $ fmap trivPrim ones
 trivPic (Picture lc ones)   = Picture lc $ fmap trivPic ones
 trivPic (Clip lc pp pic)    = Clip lc pp $ trivPic pic
-trivPic (Group lc upd pic)  = Group lc upd $ trivPic pic
 
 trivPrim :: Num u => Primitive u -> Primitive u
 trivPrim (PPath a pp)     = PPath a pp
 trivPrim (PLabel a lbl)   = PLabel a (trivLabel lbl)
 trivPrim (PEllipse a ell) = PEllipse a (trivEllipse ell)
-trivPrim (PGroup xl ones) = PGroup xl $ fmap trivPrim ones
+trivPrim (PContext a chi) = PContext a (trivPrim chi)
+trivPrim (PLink a chi)    = PLink a (trivPrim chi)
+trivPrim (PGroup ones)    = PGroup $ fmap trivPrim ones
 
 
 trivLabel :: Num u => PrimLabel u -> PrimLabel u
diff --git a/src/Wumpus/Core/Picture.hs b/src/Wumpus/Core/Picture.hs
--- a/src/Wumpus/Core/Picture.hs
+++ b/src/Wumpus/Core/Picture.hs
@@ -30,9 +30,11 @@
   , vertexPath
   , curvedPath
   , xlinkhref
-  , xlinkGroup
+  , xlink
   , primGroup
+  , primCat
 
+
   -- * Constructing primitives
   , ostroke
   , cstroke
@@ -90,7 +92,7 @@
 import Wumpus.Core.TrafoInternal
 import Wumpus.Core.Utils.Common
 import Wumpus.Core.Utils.FormatCombinators hiding ( fill )
-import Wumpus.Core.Utils.OneList
+import Wumpus.Core.Utils.JoinList
 
 import Data.AffineSpace                         -- package: vector-space
 
@@ -160,8 +162,8 @@
 -- introducing nesting with @gsave@ and @grestore@ is not likely
 -- to improve the PostScript Wumpus generates.
 --
-fontDeltaContext :: FontAttr -> Picture u -> Picture u
-fontDeltaContext fa p = Group (boundary p, []) (FontCtx fa) p
+fontDeltaContext :: FontAttr -> Primitive u -> Primitive u
+fontDeltaContext fa p = PContext (FontCtx fa) p
 
 
 -- | Create a Path from a start point and a list of PathSegments.
@@ -216,17 +218,10 @@
 xlinkhref = XLink
 
 
--- | Create a hyperlinked group of Primitives.
+-- | Create a hyperlinked Primitive.
 --
--- This function throws a runtime error when supplied with an
--- empty list.
--- 
-xlinkGroup :: XLink -> [Primitive u] -> Primitive u
-xlinkGroup _     []     = error "Picture.xlinkGroup - empty prims list"
-xlinkGroup xlink (x:xs) = PGroup (Just xlink) (step x xs)
-  where
-    step a []     = one a
-    step a (y:ys) = cons a (step y ys) 
+xlink :: XLink -> Primitive u -> Primitive u
+xlink hypl p = PLink hypl p  
 
 
 -- | Group a list of Primitives.
@@ -236,11 +231,34 @@
 --
 primGroup :: [Primitive u] -> Primitive u
 primGroup []     = error "Picture.primGroup - empty prims list"
-primGroup (x:xs) = PGroup Nothing (step x xs)
+primGroup (x:xs) = PGroup (step x xs)
   where
     step a []     = one a
     step a (y:ys) = cons a (step y ys) 
 
+
+-- | Concatenate two Primitives.
+--
+-- If both primitves are groups, then the groups are merged.
+--
+-- If one or other primitive is a group, the singleton is added
+-- into the group at the respective end.
+--
+-- Otherwise a group is formed adding both elements as /children/.
+--
+-- The Primitive type in Wumpus is a tree. In theory 'primCat' 
+-- can make flatter and wider trees than 'primGroup', though in 
+-- practice this may have no noticeable benefit as Wumpus has very 
+-- simple access patterns into the Primitive tree. 
+--
+primCat :: Primitive u -> Primitive u -> Primitive u
+primCat (PGroup a) (PGroup b) = PGroup $ join a b
+primCat (PGroup a) prim       = PGroup $ join a (one prim) 
+primCat prim       (PGroup b) = PGroup $ join (one prim) b
+primCat p1         p2         = PGroup $ join (one p1) (one p2) 
+
+
+
 --------------------------------------------------------------------------------
 -- Take Paths to Primitives
 
@@ -339,10 +357,10 @@
 --
 textlabel :: Num u 
           => RGBi -> FontAttr -> String -> Point2 u -> Primitive u
-textlabel rgb attr txt pt = rtextlabel rgb attr txt 0 pt
+textlabel rgb attr txt pt = rtextlabel rgb attr txt pt 0
 
--- | 'rtextlabel' : @ rgb * font_attr * string * rotation * 
---      baseline_left -> Primitive @
+-- | 'rtextlabel' : @ rgb * font_attr * string * baseline_left * 
+--      rotation -> Primitive @
 --
 -- Create a text label rotated by the supplied angle about the 
 -- baseline-left. 
@@ -350,8 +368,8 @@
 -- The supplied point is the left baseline.
 --
 rtextlabel :: Num u 
-           => RGBi -> FontAttr -> String -> Radian -> Point2 u -> Primitive u
-rtextlabel rgb attr txt theta pt = PLabel (LabelProps rgb attr) lbl 
+           => RGBi -> FontAttr -> String -> Point2 u -> Radian -> Primitive u
+rtextlabel rgb attr txt pt theta = PLabel (LabelProps rgb attr) lbl 
   where
     lbl = PrimLabel pt (StdLayout $ lexLabel txt) (thetaCTM theta)
 
@@ -394,6 +412,8 @@
 -- renderers. Chrome support is fine, but Firefox and Safari 
 -- currently seem lacking. 
 --
+-- Also, currently the generated PostScript is inefficient.
+--
 hkernlabel :: Num u 
             => RGBi -> FontAttr -> [KerningChar u] -> Point2 u 
             -> Primitive u
@@ -432,6 +452,8 @@
 -- renderers. Chrome support is fine, but Firefox and Safari 
 -- currently seem lacking. 
 --
+-- Also, currently the generated PostScript is inefficient.
+--
 vkernlabel :: Num u 
             => RGBi -> FontAttr -> [KerningChar u] -> Point2 u 
             -> Primitive u
@@ -595,11 +617,11 @@
 -- neither picture will be moved.
 --
 picOver :: (Num u, Ord u) => Picture u -> Picture u -> Picture u
-a `picOver` b = Picture (bb,[]) (cons b $ one a) 
+a `picOver` b = Picture (bb,[]) (join (one b) (one a))   
   where
     bb = boundary a `boundaryUnion` boundary b
 
--- picOver note - draw b, put b first in the list, so it draws 
+-- NOTE - picOver - draw b, put b first in the list, so it draws 
 -- first in the output (this is also @behind@ in the Z-Order).
 
 
diff --git a/src/Wumpus/Core/PictureInternal.hs b/src/Wumpus/Core/PictureInternal.hs
--- a/src/Wumpus/Core/PictureInternal.hs
+++ b/src/Wumpus/Core/PictureInternal.hs
@@ -66,7 +66,7 @@
 import Wumpus.Core.TrafoInternal
 import Wumpus.Core.Utils.Common
 import Wumpus.Core.Utils.FormatCombinators
-import Wumpus.Core.Utils.OneList
+import Wumpus.Core.Utils.JoinList
 
 
 import Data.AffineSpace                         -- package: vector-space
@@ -110,25 +110,15 @@
 -- updates for the SVG renderer - in some instances this can 
 -- improve the code size of the generated SVG.
 --
-data Picture u = Leaf     (Locale u)              (OneList (Primitive u))
-               | Picture  (Locale u)              (OneList (Picture u))
+data Picture u = Leaf     (Locale u)              (JoinList (Primitive u))
+               | Picture  (Locale u)              (JoinList (Picture u))
                | Clip     (Locale u) (PrimPath u) (Picture u)
-               | Group    (Locale u) FontCtx      (Picture u)
   deriving (Show)
 
 type DPicture = Picture Double
 
 
--- | Set the font /delta/ for SVG rendering. 
--- 
--- Note - this does not change the default colour or font style. 
--- It is solely a backdoor into the SVG renderer to potential 
--- allow some code size reductions.
---
-newtype FontCtx = FontCtx { getFontCtx :: FontAttr }
-  deriving (Eq,Show)
 
-
 -- | Locale = (bounding box * current translation matrix)
 -- 
 -- Pictures (and sub-pictures) are located frame consisting of a 
@@ -173,18 +163,36 @@
 -- Though typically for affine transformations a Fractional 
 -- constraint is also obliged.
 --
--- To represent XLink hyperlinks, Primitives can be grouped 
--- together at the same type (so Primitives aren\'t strictly)
--- /primitive/ as the actual implementation is a tree.
+-- To represent XLink hyperlinks, Primitives can be annotated 
+-- with some a hyperlink (similarly a a font change for better
+-- SVG code generation) and grouped - a hyperlinked arrow would
+-- want the tip and the arrow body both to be incorporated in the
+-- link even though they are two drawings. 
+--
+-- This means that Primitives aren\'t strictly /primitive/ as 
+-- the actual implementation is a tree.
 -- 
 data Primitive u = PPath    PathProps     (PrimPath u)
                  | PLabel   LabelProps    (PrimLabel u)
                  | PEllipse EllipseProps  (PrimEllipse u)
-                 | PGroup   (Maybe XLink) (OneList (Primitive u))
+                 | PContext FontCtx       (Primitive u)
+                 | PLink    XLink         (Primitive u)
+                 | PGroup   (JoinList (Primitive u))
   deriving (Eq,Show)
 
+
 type DPrimitive = Primitive Double
 
+
+-- | Set the font /delta/ for SVG rendering. 
+-- 
+-- Note - this does not change the default colour or font style. 
+-- It is solely a backdoor into the SVG renderer to potential 
+-- allow some code size reductions.
+--
+newtype FontCtx = FontCtx { getFontCtx :: FontAttr }
+  deriving (Eq,Show)
+
 -- | Primitives can be grouped with hyperlinks in SVG output.
 --
 newtype XLink = XLink { getXLink :: String }
@@ -305,12 +313,8 @@
                                               , format path
                                               , format pic  ]
 
-  format (Group m _ pic)    = indent 2 $ vcat [ text "** Group **"
-                                              , fmtLocale m
-                                              , format pic  ]
 
-
-fmtPics :: PSUnit u => OneList (Picture u) -> Doc
+fmtPics :: PSUnit u => JoinList (Picture u) -> Doc
 fmtPics ones = snd $ F.foldl' fn (0,empty) ones
   where
     fn (n,acc) e = (n+1, vcat [ acc, text "-- " <+> int n, format e, line])
@@ -330,11 +334,17 @@
   format (PEllipse props e) = 
       indent 2 $ vcat [ text "ellipse:" <+> format props, format e ]
 
-  format (PGroup xl ones)   = 
-      vcat [ text "-- group " <+> (maybe empty format xl), fmtPrimlist ones  ]
+  format (PContext _ a)     = 
+      vcat [ text "-- svg ctx change " , format a ]
 
+  format (PLink _ a)     = 
+      vcat [ text "-- svg link " , format a ]
 
-fmtPrimlist :: PSUnit u => OneList (Primitive u) -> Doc
+  format (PGroup ones)      = 
+      vcat [ text "-- group ", fmtPrimlist ones  ]
+
+
+fmtPrimlist :: PSUnit u => JoinList (Primitive u) -> Doc
 fmtPrimlist ones = snd $ F.foldl' fn (0,empty) ones
   where
     fn (n,acc) e = (n+1, vcat [ acc, text "-- leaf" <+> int n, format e, line])
@@ -381,14 +391,15 @@
   boundary (Leaf    (bb,_) _)   = bb
   boundary (Picture (bb,_) _)   = bb
   boundary (Clip    (bb,_) _ _) = bb
-  boundary (Group   (bb,_) _ _) = bb
 
 
 instance (Real u, Floating u, FromPtSize u) => Boundary (Primitive u) where
   boundary (PPath _ p)      = pathBoundary p
   boundary (PLabel a l)     = labelBoundary (label_font a) l
   boundary (PEllipse _ e)   = ellipseBoundary e
-  boundary (PGroup _ ones)  = outer $ viewl ones 
+  boundary (PContext _ a)   = boundary a
+  boundary (PLink _ a)      = boundary a
+  boundary (PGroup ones)    = outer $ viewl ones 
     where
       outer (OneL a)     = boundary a
       outer (a :< as)    = inner (boundary a) (viewl as)
@@ -526,7 +537,6 @@
 mapLocale f (Leaf lc ones)     = Leaf (f lc) ones
 mapLocale f (Picture lc ones)  = Picture (f lc) ones
 mapLocale f (Clip lc pp pic)   = Clip (f lc) pp pic
-mapLocale f (Group lc upd pic) = Group (f lc) upd pic
 
 
 --------------------------------------------------------------------------------
@@ -542,28 +552,36 @@
   rotate r (PPath a path)   = PPath a    $ rotatePath r path
   rotate r (PLabel a lbl)   = PLabel a   $ rotateLabel r lbl
   rotate r (PEllipse a ell) = PEllipse a $ rotateEllipse r ell
-  rotate r (PGroup xln xs)  = PGroup xln $ fmap (rotate r) xs
+  rotate r (PContext a chi) = PContext a $ rotate r chi 
+  rotate r (PLink a chi)    = PLink a    $ rotate r chi 
+  rotate r (PGroup xs)      = PGroup     $ fmap (rotate r) xs
  
 
 instance (Real u, Floating u) => RotateAbout (Primitive u) where
   rotateAbout r pt (PPath a path)   = PPath a    $ rotateAboutPath r pt path
   rotateAbout r pt (PLabel a lbl)   = PLabel a   $ rotateAboutLabel r pt lbl
   rotateAbout r pt (PEllipse a ell) = PEllipse a $ rotateAboutEllipse r pt ell
-  rotateAbout r pt (PGroup xln xs)  = PGroup xln $ fmap (rotateAbout r pt) xs
+  rotateAbout r pt (PContext a chi) = PContext a $ rotateAbout r pt chi
+  rotateAbout r pt (PLink a chi)    = PLink a    $ rotateAbout r pt chi
+  rotateAbout r pt (PGroup xs)      = PGroup     $ fmap (rotateAbout r pt) xs
 
 
 instance Num u => Scale (Primitive u) where
   scale sx sy (PPath a path)    = PPath a    $ scalePath sx sy path
   scale sx sy (PLabel a lbl)    = PLabel a   $ scaleLabel sx sy lbl
   scale sx sy (PEllipse a ell)  = PEllipse a $ scaleEllipse sx sy ell
-  scale sx sy (PGroup xln xs)   = PGroup xln $ fmap (scale sx sy) xs
+  scale sx sy (PContext a chi)  = PContext a $ scale sx sy chi
+  scale sx sy (PLink a chi)     = PLink a    $ scale sx sy chi
+  scale sx sy (PGroup xs)       = PGroup     $ fmap (scale sx sy) xs
 
 
 instance Num u => Translate (Primitive u) where
   translate dx dy (PPath a path)   = PPath a    $ translatePath dx dy path
   translate dx dy (PLabel a lbl)   = PLabel a   $ translateLabel dx dy lbl
   translate dx dy (PEllipse a ell) = PEllipse a $ translateEllipse dx dy ell
-  translate dx dy (PGroup xln xs)  = PGroup xln $ fmap (translate dx dy) xs
+  translate dx dy (PContext a chi) = PContext a $ translate dx dy chi
+  translate dx dy (PLink a chi)    = PLink a    $ translate dx dy chi
+  translate dx dy (PGroup xs)      = PGroup     $ fmap (translate dx dy) xs
 
 
 --------------------------------------------------------------------------------
diff --git a/src/Wumpus/Core/PtSize.hs b/src/Wumpus/Core/PtSize.hs
--- a/src/Wumpus/Core/PtSize.hs
+++ b/src/Wumpus/Core/PtSize.hs
@@ -38,7 +38,7 @@
 -- etc.
 -- 
 newtype PtSize = PtSize { ptSize :: Double } 
-  deriving (Eq,Ord,Num,Floating,Fractional)
+  deriving (Eq,Ord,Num,Floating,Fractional,Real,RealFrac,RealFloat)
 
 instance Show PtSize where
   showsPrec p d = showsPrec p (ptSize d)
diff --git a/src/Wumpus/Core/Utils/JoinList.hs b/src/Wumpus/Core/Utils/JoinList.hs
new file mode 100644
--- /dev/null
+++ b/src/Wumpus/Core/Utils/JoinList.hs
@@ -0,0 +1,240 @@
+{-# OPTIONS -Wall #-}
+
+--------------------------------------------------------------------------------
+-- |
+-- Module      :  Wumpus.Core.Utils.JoinList
+-- Copyright   :  (c) Stephen Tetley 2010
+-- License     :  BSD3
+--
+-- A \"join list\" datatype and operations. 
+--
+-- A join list is implemented a binary tree, so joining two 
+-- lists (catenation, aka (++)) is a cheap operation. 
+--
+-- This constrasts with the regular list datatype which is a 
+-- cons list: while consing on a regular list is by nature cheap, 
+-- joining (++) is expensive. 
+--
+-- This version has no Empty constructor, so empty join lists 
+-- cannot be built.
+--
+--------------------------------------------------------------------------------
+
+
+module Wumpus.Core.Utils.JoinList 
+  ( 
+  -- * Join list datatype, opaque.
+    JoinList
+
+  -- * Left view as per Data.Sequence  
+  , ViewL(..)
+
+  -- * Conversion between join lists and regular lists
+  , fromList
+  , toList
+  , toListF
+
+  -- * Construction
+  , one
+  , cons
+  , snoc
+  , join
+
+  -- * Basic functions  
+  , head
+
+  , accumMapL
+  , isOne
+  , isMany
+
+  -- * Left view
+  , viewl
+
+
+  
+  ) where
+
+
+import Control.Applicative hiding ( empty )
+
+import Data.Foldable ( Foldable )
+import qualified Data.Foldable as F
+import Data.Monoid ( mappend )
+import Data.Traversable ( Traversable(..) )
+
+import Prelude hiding ( head )
+
+data JoinList a = One a 
+                | Join (JoinList a) (JoinList a)
+  deriving (Eq)
+
+data ViewL a = OneL a | a :< (JoinList a)
+  deriving (Eq,Show)
+
+
+--------------------------------------------------------------------------------
+
+instance Show a => Show (JoinList a) where
+  showsPrec _ xs = showString "fromList " . shows (toList xs) 
+
+
+instance Functor JoinList where
+  fmap f (One a)    = One (f a)
+  fmap f (Join t u) = Join (fmap f t) (fmap f u)
+
+
+
+instance Foldable JoinList where
+  foldMap f (One a)    = f a
+  foldMap f (Join t u) = F.foldMap f t `mappend` F.foldMap f u
+
+  foldr                = joinfoldr
+  foldl                = joinfoldl
+
+instance Traversable JoinList where
+  traverse f (One a)    = One <$> f a
+  traverse f (Join t u) = Join <$> traverse f t <*> traverse f u
+
+-- Views
+
+instance Functor ViewL where
+  fmap f (OneL a)       = OneL $ f a
+  fmap f (a :< as)      = f a :< fmap f as
+
+
+--------------------------------------------------------------------------------
+-- Conversion
+
+-- | Convert a join list to a regular list.
+--
+toList :: JoinList a -> [a]
+toList = joinfoldl (flip (:)) []
+
+-- | Build a join list from a regular list.
+--
+-- This builds a tall skinny list.
+--
+-- WARNING - throws an error on empty list.
+--
+
+fromList :: [a] -> JoinList a
+fromList []     = error "Wumpus.Core - internal error empty JoinList"
+fromList [x]    = One x
+fromList (x:xs) = Join (One x) (fromList xs)
+
+
+-- Note -- this works from Right to left...
+--
+toListF :: (a -> b) -> JoinList a -> [b]
+toListF f = step []
+  where
+    step acc (One x)     = f x : acc
+    step acc (Join t u)  = let acc' = step acc u in step acc' t
+
+
+
+--------------------------------------------------------------------------------
+
+isOne :: JoinList a -> Bool
+isOne (One _)       = True
+isOne _             = False
+
+isMany :: JoinList a -> Bool
+isMany (Join _ _)   = True
+isMany _            = False
+
+
+
+
+-- | Create a singleton join list.
+--
+one :: a -> JoinList a
+one = One
+
+
+-- | Cons an element to the front of the join list.
+--
+cons :: a -> JoinList a -> JoinList a
+cons a xs = Join (One a) xs  
+
+-- | Snoc an element to the tail of the join list.
+--
+snoc :: JoinList a -> a -> JoinList a
+snoc xs a = Join xs (One a)
+
+
+
+
+infixr 5 `join`
+
+-- | Because there is no empty join list, join is Join.
+--
+join :: JoinList a -> JoinList a -> JoinList a
+join = Join
+
+--------------------------------------------------------------------------------
+-- Basic functions
+
+-- | Extract the first element of a join list - i.e. the leftmost
+-- element of the left spine. An error is thrown if the list is 
+-- empty. 
+-- 
+-- This function performs a traversal down the left spine, so 
+-- unlike @head@ on regular lists this function is not performed 
+-- in constant time.
+--
+head :: JoinList a -> a
+head (One a)    = a
+head (Join t _) = head t
+
+
+
+
+accumMapL :: (x -> st -> (y,st)) -> JoinList x -> st -> (JoinList y,st)
+accumMapL f xs st0 = go xs st0 
+  where
+    go (One x)     st = let (y,st') = f x st in (One y,st')
+    go (Join t u)  st = (Join v w, st'')
+                             where (v,st')  = go t st
+                                   (w,st'') = go u st'
+
+
+
+
+-- | Right-associative fold of a JoinList.
+--
+joinfoldr :: (a -> b -> b) -> b -> JoinList a -> b
+joinfoldr f = go
+  where
+    go e (One a)    = f a e
+    go e (Join t u) = go (go e t) u
+
+
+-- | Left-associative fold of a JoinList.
+--
+joinfoldl :: (b -> a -> b) -> b -> JoinList a -> b
+joinfoldl f = go 
+  where
+    go e (One a)    = f e a
+    go e (Join t u) = go (go e u) t
+
+--------------------------------------------------------------------------------
+-- Views
+
+-- | Access the left end of a sequence.
+--
+-- Unlike the corresponing operation on Data.Sequence this is 
+-- not a cheap operation, the joinlist must be traversed down 
+-- the left spine to find the leftmost node.
+--
+-- Also the traversal may involve changing the shape of the 
+-- underlying binary tree.
+--
+viewl :: JoinList a -> ViewL a
+viewl (One a)    = OneL a
+viewl (Join t u) = step t u
+  where
+    step (One a)      r = a :< r
+    step (Join t' u') r = step t' (Join u' r)
+
+
diff --git a/src/Wumpus/Core/Utils/OneList.hs b/src/Wumpus/Core/Utils/OneList.hs
deleted file mode 100644
--- a/src/Wumpus/Core/Utils/OneList.hs
+++ /dev/null
@@ -1,133 +0,0 @@
-{-# OPTIONS -Wall #-}
-
---------------------------------------------------------------------------------
--- |
--- Module      :  Wumpus.Core.Utils.OneList
--- Copyright   :  (c) Stephen Tetley 2009-2010
--- License     :  BSD3
---
--- Maintainer  :  Stephen Tetley <stephen.tetley@gmail.com>
--- Stability   :  highly unstable
--- Portability :  GHC
---
--- Data type for non-empty lists.
--- 
---------------------------------------------------------------------------------
-
-module Wumpus.Core.Utils.OneList
-  (
-   -- OneMany
-    OneList
-  , ViewL(..)
-
-  , one
-  , cons
-  , head
-  , viewl
-
-  , fromList
-
-  , toListF
-  , accumMapL
-  , isOne
-  , isMany
-   
-  ) where
-
-
-
-import Control.Applicative
-import Data.Foldable
-import Data.Monoid
-import Data.Traversable
-
-import Prelude hiding ( head )
-
-
-data OneList a = One a | Many a (OneList a)
-  deriving (Eq)
-
-data ViewL a = OneL a | a :< (OneList a)
-  deriving (Eq)
-
-
-
---------------------------------------------------------------------------------
--- Instances
-
-instance Show a => Show (OneList a) where
-  show = ('{':) . ($ []) . step where
-     step (One a)     = shows a . showChar '}'
-     step (Many a as) = shows a . showChar ',' . step as
-
-
-instance Functor OneList where
-  fmap f (One a)        = One $ f a
-  fmap f (Many a as)    = Many (f a) (fmap f as)
-
-instance Foldable OneList where
-  foldMap f (One a)     = f a
-  foldMap f (Many a as) = f a `mappend` foldMap f as
-
-  foldr f b0 = step b0 where
-    step b (One a)      = f a b
-    step b (Many a as)  = f a (step b as)
-
-  foldl f b0 = step b0 where
-    step b (One a)      = f b a
-    step b (Many a as)  = step (f b a) as
-
-
-instance Traversable OneList where
-  traverse f (One a)      = One  <$> f a
-  traverse f (Many a as)  = Many <$> f a <*> traverse f as
-
-
-
---------------------------------------------------------------------------------
--- | Construct One.
-one :: a -> OneList a
-one = One
-
-
--- | Prepend an element. Obviously this transforms a One to a Many.
-cons :: a -> OneList a -> OneList a
-cons a as   = Many a as
-
--- | 'head' is total of course.
-head :: OneList a -> a
-head (One a)    = a
-head (Many a _) = a
-
-viewl :: OneList a -> ViewL a
-viewl (One a)     = OneL a
-viewl (Many a as) = a :< as
-
--- | Construct Many. Not this function throws a error if the list has
--- zero or one elements
-fromList :: [a] -> OneList a
-fromList []     = error "OneList.fromList: cannot build Many from empty list"
-fromList [a]    = One a
-fromList (a:as) = Many a (fromList as)
-
-
-toListF :: (a -> b) -> OneList a -> [b]
-toListF f = step where
-  step (One x)     = [f x]
-  step (Many x xs) = f x : step xs
-
-
-accumMapL :: (x -> st -> (y,st)) -> OneList x -> st -> (OneList y,st)
-accumMapL f (One x)     st = let (y,st') = f x st in (One y,st')
-accumMapL f (Many x xs) st = (Many y ys,st'')
-                             where (y, st')  = f x st
-                                   (ys,st'') = accumMapL f xs st'
-
-isMany :: OneList a -> Bool
-isMany (Many _ _) = True
-isMany _          = False
-
-isOne :: OneList a -> Bool
-isOne (One _)     = True
-isOne _           = False
-
diff --git a/src/Wumpus/Core/VersionNumber.hs b/src/Wumpus/Core/VersionNumber.hs
--- a/src/Wumpus/Core/VersionNumber.hs
+++ b/src/Wumpus/Core/VersionNumber.hs
@@ -22,7 +22,7 @@
 
 -- | Version number.
 --
--- > (0,36,0)
+-- > (0,37,0)
 --
 wumpus_core_version :: (Int,Int,Int)
-wumpus_core_version = (0,36,0)
+wumpus_core_version = (0,37,0)
diff --git a/wumpus-core.cabal b/wumpus-core.cabal
--- a/wumpus-core.cabal
+++ b/wumpus-core.cabal
@@ -1,5 +1,5 @@
 name:             wumpus-core
-version:          0.36.0
+version:          0.37.0
 license:          BSD3
 license-file:     LICENSE
 copyright:        Stephen Tetley <stephen.tetley@gmail.com>
@@ -38,82 +38,49 @@
   the design permits a fairly simple implementation, which is a 
   priority. 
   .  
+  NOTE version 0.37.0 - there will be no release of Wumpus-Basic
+  to match this release of Wumpus-Core. Wumpus-Basic is 
+  undergoing substantial change to accommodate glyph metrics and
+  thus enable proper text bounding boxes and right and center
+  aligned text. The improvements to Wumpus-Core merit a release
+  so that there is not a large hiatus between the APIs of the 
+  Hackage published latest version and the SVN repository.
   .
+  .
   \[1\] Because the output is simple, straight-line PostScript 
   code, it is possible to use GraphicsMagick or a similar tool 
   to convert EPS files generated by Wumpus to many other formats 
   (bitmaps). 
   .
-  VERSION 0.36.0 UPGRADE NOTES
   .
-  There are two major changes between 0.35.0 and 0.36.0. 
-  .
-  @PrimElement@ has been removed and the grouping constructor it 
-  provided has been moved into the @Primitive@ type. As both 
-  types are opaque, definitions in client code will work without 
-  change, /but all/ type signatures referencing @PrimElement@ will 
-  need to replace @PrimElement@ with @Primitive@.
-  .
-  Rotations and scalings on Primitives have changed again.
-  Primitives are now instances of the affine classes so support - 
-  @rotate@, @rotateAbout@, @scale@, @translate@. Primitives are 
-  now considered to be in the implicit affine frame with origin at 
-  (0,0). Previously rotatation on Primitives (via the function 
-  @rotatePrim@) was really a special case to allow slanted text, 
-  the rotation was about the text\'s baseline origin and not the 
-  affine frame. As rotation now works differently there is a 
-  special constructor for slanted text @rtextlabel@.
-  .
   Changelog:
-  .
-  0.35.0 to 0.36.0:
-  .
-  * API / behaviour change - rotation on primitives changed. New 
-    functions have been added to create rotated text labels and 
-    ellipses (@rtextlabel@, @rstrokeEllipse@, etc.), and 
-    Primitives have been made instances of the Affine classes
-    except for the general matrix Transform class. The old
-    functions for transforming Primitives (@rotatePrim@, 
-    @scalePrim@, etc.) have been removed. The demos (Rotated.hs,
-    Scaled.hs, Translated.hs) have been removed as they pertain 
-    to the old behaviour, there are new demos highlighting the
-    new behaviour (TransformEllipse.hs, etc.).
-  .
-  * Major change - removed the PrimElement type. The (opaque) 
-    Primitive type has been changed to incorporate a grouping 
-    constructor equivalent to PrimElement\'s @XLinkGroup@ 
-    contructor. The change has made the implementation of SVG 
-    hyperlinks more efficient, but has forced various type 
-    signatures to change in @Core.Picture@. Client code will 
-    also have to change type signatures - @PrimElement@ becomes
-    @Primitive@.
-  .
-  * @Core.PtSize@ - the class @FromPtSize@ has been given a @Num@
-    superclass constraint. This can shorten type signatures of 
-    functions that use @fromPtSize@.
-  .
-  * Corrected a bug where textlabels would generate an invalid
-    bounding box and cause a runtime error when supplied with an
-    empty string. Now there is no runtime error - and /no-ops/ 
-    are generated in the output.
+  . 
+  0.36.0 to 0.37.0:
   .
-  * Internal changes - moved @PrimCTM@ from @Core.PictureInternal@
-    into separate module. Moved /utility/ modules into their own 
-    directory @Utils@. Move /text/ modules into their own 
-    directory @Text@. 
+  * The bounding box constructors have been renamed - @bbox@ is 
+    now @boundingBox@ and @obbox@ becomes @oboundingBox@. The 
+    rationale for this change is that the names very cryptic in 
+    the first place and the constructors are used infrequently 
+    when @bbox@ in particular makes a descriptive variable name.
   .
-  * Removed dependency on @algebra@ for @Semigroup@. The 
-    equivalent @append@ operation on @BoundingBox@ is 
-    @boundaryUnion@.
+  * Changes to the Picture and Primitive types to enable better
+    concatenation which is used heavily by Wumpus-Basic. The 
+    Picture API exposes a new function @primCat@.
   .
-  * Renamed the @Core.GraphicsState@ to @Core.GraphicProps@. 
-    Moved the property datatypes from @Core.PictureInternal@ into 
-    @Core.GraphicProps@ (StrokeProps, LabelProps, etc.).
+  * SVG /font delta context/ change - font deltas are now 
+    annotated on Primitives not Pictures. The type of the 
+    function @fontDeltaContext@ in @Core.Picture@ has changed 
+    accordingly.
   .
-  * Moved @wumpus_default_font@ from @Core.Picture@ into 
-    @Core.Graphic.Props@.
+  * SVG hyperlink change - hyperlinks no longer group primitives
+    (although a group of primitives can be hyperlinked). The 
+    function @xlinkGroup@ has been removed from @Core.Picture@, 
+    it is replaced by @xlink@. Primitives are now grouped with the
+    function @primGroup@.
   .
-  * Haddock docs improved.
+  * @Core.Picture@ - the argument order for the function 
+    @rtextlabel@ has been changed, the positions of the angle and 
+    bottom-left corner have been swapped.
   .
   .
 build-type:         Simple
@@ -178,7 +145,7 @@
     Wumpus.Core.Text.TextInternal,
     Wumpus.Core.TrafoInternal,
     Wumpus.Core.Utils.Common,
-    Wumpus.Core.Utils.OneList,
+    Wumpus.Core.Utils.JoinList,
     Wumpus.Core.Utils.FormatCombinators
     
   extensions: