diff --git a/SketchWidget.py b/SketchWidget.py
index cd711e7..84b92fc 100644
--- a/SketchWidget.py
+++ b/SketchWidget.py
@@ -11,6 +11,9 @@ from Circle import Circle
 class SketchWidget:
     def __init__(self, sketch):
         self.sketch = sketch
+        self.view_center = (0, 0)
+        self.view_width = 5.0
+        self.size = (1, 1)
         try:
             # try double-buffered
             self.glconfig = gtk.gdkgl.Config(mode = (gtk.gdkgl.MODE_RGB |
@@ -51,10 +54,11 @@ class SketchWidget:
         if not gldrawable.gl_begin(glcontext): return
 
         x, y, width, height = glarea.get_allocation()
+        self.size = (width, height)
 
         glViewport(0, 0, width, height)
         glMatrixMode(GL_PROJECTION)
-        glOrtho(-2, 2, -1.5, 1.5, 1.0, -1.0)
+        glOrtho(0, width, 0, height, 1.0, -1.0)
 
         glMatrixMode(GL_MODELVIEW)
         glLoadIdentity()
@@ -75,9 +79,9 @@ class SketchWidget:
 
         for shape in self.sketch:
             if isinstance(shape, Line):
-                self.drawLine(shape, 0.03)
+                self.drawLine(shape, 1.5)
             elif isinstance(shape, Circle):
-                self.drawCircle(shape, 0.03)
+                self.drawCircle(shape, 1.5)
 
         if gldrawable.is_double_buffered():
             gldrawable.swap_buffers()
@@ -88,16 +92,26 @@ class SketchWidget:
 
         return True
 
+    def ptToScreenPt(self, pt):
+        return ((pt[0] - self.view_center[0]) / self.view_width * self.size[0]
+                    + self.size[0] / 2,
+                (pt[1] - self.view_center[1]) /
+                    (self.view_width * self.size[1] / self.size[0]
+                        * self.size[1] + self.size[1] / 2))
+
+    def distToScreenDist(self, dist):
+        return dist / self.view_width * self.size[0]
+
     def drawLine(self, shape, size):
-        pt0 = shape.getPt(0)
-        pt1 = shape.getPt(1)
+        pt0 = self.ptToScreenPt(shape.getPt(0))
+        pt1 = self.ptToScreenPt(shape.getPt(1))
         self.drawFilledLine(pt0[0], pt0[1], pt1[0], pt1[1], size)
 
     def drawCircle(self, shape, size):
         steps = 16
         step = 2 * math.pi / steps
-        center = shape.getCenter()
-        rad = shape.getRadius()
+        center = self.ptToScreenPt(shape.getCenter())
+        rad = self.distToScreenDist(shape.getRadius())
         for i in range(steps + 1):
             angle = i * step
             next_angle = (i + 1) * step