diff --git a/demo.scm b/demo.scm
index 57dbdae..6e52074 100644
--- a/demo.scm
+++ b/demo.scm
@@ -1,19 +1,10 @@
-(use-modules (graphgif))
+(use-modules (graphgif)
+	     (srfi srfi-9 gnu)
+	     (ice-9 copy-tree))
 
 (define red (create-color 1 0 0))
 
-(define my-graph
-  `(((10 . 10) (1))
-    ((30 . 20) () ,red)))
-
-(define more-complex-graph
-  `(((10 . 10) ()) 
-    ((40 . 10) (0))
-    ((25 . 25) (0 1))
-    ((10 . 40) (0 2 4))
-    ((40 . 40) (1 2 3))))
-
-(let* ([graph1 (generate-web 10 10)]
-       [graph2 (list-copy graph1)])
-  (set-car! graph2 (append (car graph2) `(,red)))
-  (write-graphs-to-file (list graph1 graph2) "graph.gif"))
+(define graph1 (generate-web 10 10))
+(define graph2 (copy-tree graph1))
+(assq-set! graph2 0 (set-node-color (assq-ref graph2 0) red))
+(write-graphs-to-file (list graph1 graph2) "graph.gif")
diff --git a/graphgif.scm b/graphgif.scm
index 8b3101e..2ee0759 100644
--- a/graphgif.scm
+++ b/graphgif.scm
@@ -1,7 +1,8 @@
 (define-module (graphgif))
 
 (use-modules (cairo)
-	     (srfi srfi-1))
+	     (srfi srfi-1)
+	     (srfi srfi-9 gnu))
 
 (re-export (cairo-pattern-create-rgb . create-color))
 
@@ -15,17 +16,28 @@
 (define-public black (cairo-pattern-create-rgb 0 0 0))
 (define-public white (cairo-pattern-create-rgb 1 1 1))
 
+(define-immutable-record-type <node>
+  (node coords edges color)
+  node?
+  (coords node-coords set-node-coords)
+  (edges node-edges set-node-edges)
+  (color node-color set-node-color))
+(export node node?
+	node-coords set-node-coords
+	node-edges set-node-edges
+	node-color set-node-color)
+
 (define (edge-painter cr graph)
   (lambda (node)
     (cairo-set-source cr black)
-    (let ([x (caar node)]
-	  [y (cdar node)]
-	  [edges (cadr node)])
+    (let ([x (car (node-coords node))]
+	  [y (cdr (node-coords node))]
+	  [edges (node-edges node)])
       (for-each
        (lambda (edge)
-	 (let* ([other (list-ref graph edge)]
-		[ox (caar other)]
-		[oy (cdar other)])
+	 (let* ([other (assq-ref graph edge)]
+		[ox (car (node-coords other))]
+		[oy (cdr (node-coords other))])
 	   (cairo-move-to cr x y)
 	   (cairo-line-to cr ox oy)
 	   (cairo-stroke cr)))
@@ -33,11 +45,9 @@
 
 (define (node-painter cr)
   (lambda (node)
-    (let ([x (caar node)]
-	  [y (cdar node)]
-	  [color (if (null? (cddr node))
-		     white
-		     (caddr node))])
+    (let ([x (car (node-coords node))]
+	  [y (cdr (node-coords node))]
+	  [color (or (node-color node) white)])
       (cairo-arc cr x y 4. 0. tau)
       (cairo-set-source cr color)
       (cairo-fill-preserve cr)
@@ -53,8 +63,8 @@
     (cairo-rectangle cr 0 0 400 400)
     (cairo-set-source cr white)
     (cairo-fill cr)
-    (for-each paint-edges graph)
-    (for-each paint-nodes graph)
+    (for-each paint-edges (map cdr graph))
+    (for-each paint-nodes (map cdr graph))
     (cairo-destroy cr)
     surface))
 
@@ -91,10 +101,12 @@
 
 (define-public (generate-web w h)
   (define (make-node i)
-    (list
-     (cons (+ (* 30 (idx->x i w)) 10)
-	   (+ (* 30 (idx->y i w)) 10))
-     (idx->edges i w)))
+    (cons i
+	  (node
+	   (cons (+ (* 30 (idx->x i w)) 10)
+		 (+ (* 30 (idx->y i w)) 10))
+	   (idx->edges i w)
+	   #f)))
   (let loop ([i 0]
 	     [lst '()])
     (if (>= i (* w h))
@@ -106,7 +118,7 @@
 ;;;;;;;;;;;;
 
 (define (output-to-file surfaces filename)
-  (define pngdir (mkdtemp "graphgif_XXXXXX"))
+  (define pngdir (mkdtemp "/tmp/graphgif_XXXXXX"))
   (do ([i 1 (1+ i)]
        [surfaces surfaces (cdr surfaces)])
       ((null? surfaces))