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diff --git a/src/core/affine.lisp b/src/core/affine.lisp
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+++ b/src/core/affine.lisp
@@ -0,0 +1,69 @@
+;;;; affine.lisp
+
+(in-package #:wheelwork)
+
+(defclass/std affine (unit)
+  ((cached-model cached-projected-matrix cached-application :a)
+   (base-width base-height :r :std 1.0 :doc "Determined by content.")
+   (scale-x scale-y :std 1.0)
+   (rotation x y :std 0.0)))
+
+(defmethod (setf closer-mop:slot-value-using-class) :after
+    (newval class (affine affine) slot)
+  (case (closer-mop:slot-definition-name slot)
+    ((x y scale-x scale-y rotation)
+     (setf (cached-model affine) nil
+           (cached-projected-matrix affine) nil))))
+
+(defun scale-by (affine amount)
+  (with-slots (scale-x scale-y) affine
+    (setf scale-x (* amount scale-x)
+          scale-y (* amount scale-y))))
+
+(defun set-width-preserve-aspect (affine new-width)
+  (scale-by affine (/ new-width (width affine))))
+
+(defun set-height-preserve-aspect (affine new-height)
+  (scale-by affine (/ new-height (height affine) )))
+
+(defun width (affine)
+  (with-slots (scale-x base-width) affine
+    (* scale-x base-width)))
+
+(defun height (affine)
+  (with-slots (scale-y base-height) affine
+    (* scale-y base-height)))
+
+(defun (setf width) (newval affine)
+  (with-slots (scale-x base-width) affine
+    (setf scale-x (coerce (/ newval base-width) 'single-float))))
+
+(defun (setf height) (newval affine)
+  (with-slots (scale-y base-height) affine
+    (setf scale-y (coerce (/ newval base-height) 'single-float))))
+
+(defmethod model-matrix :around ((u affine))
+  (or (cached-model u)
+      (setf (cached-model u)
+            (call-next-method))))
+
+(defmethod model-matrix ((u affine))
+  (let ((m (mat:meye 4)))
+    (with-slots (x y base-width scale-x base-height scale-y rotation) u 
+      (let ((uw (* base-width scale-x))
+            (uh (* base-height scale-y)))
+        (mat:nmtranslate m (vec:vec x y 0.0))
+
+        (mat:nmtranslate m (vec:v* 0.5 (vec:vec uw uh 0.0)))
+        (mat:nmrotate  m vec:+vz+ rotation)
+        (mat:nmtranslate m (vec:v* -0.5 (vec:vec uw uh 0.0)))
+        
+        (mat:nmscale m (vec:vec uw uh 1.0))))
+    m))
+
+
+(defun projected-matrix (affine)
+  (or (cached-projected-matrix affine)
+      (setf (cached-projected-matrix affine)
+            (mat:marr (mat:m* (application-projection (app-of-unit affine))
+                              (model-matrix affine))))))