diff --git a/SketchWidget.py b/SketchWidget.py
index c97af0e..cf23799 100644
--- a/SketchWidget.py
+++ b/SketchWidget.py
@@ -18,6 +18,7 @@ class SketchWidget:
         self.panning = False
         self.drawingLine = None
         self.drawingCircle = None
+        self.mode = ''
 
         # Configuration parameters
         self.line_width = 1.5
@@ -222,29 +223,31 @@ class SketchWidget:
 
     def button_press_event(self, widget, event, data = None):
         if event.button == 1:
-            start = self.screenPtToPt((event.x, self.size[1] - event.y))
-            if self.drawingLine is not None:
-                self.sketch.shapes.append(self.drawingLine)
-                if self.drawingLine.getPt(0)[0] == self.drawingLine.getPt(1)[0]:
-                    self.sketch.constraints.append(
-                            Vertical(self.drawingLine, 0,
-                                self.drawingLine, 1))
-                elif (self.drawingLine.getPt(0)[1]
-                        == self.drawingLine.getPt(1)[1]):
-                    self.sketch.constraints.append(
-                            Horizontal(self.drawingLine, 0,
-                                self.drawingLine, 1))
-                start = self.drawingLine.getPt(1)
-            self.drawingLine = Line(start[0], start[1], start[0], start[1])
-            self.queue_redraw()
+            if self.mode == 'line':
+                start = self.screenPtToPt((event.x, self.size[1] - event.y))
+                if self.drawingLine is not None:
+                    self.sketch.shapes.append(self.drawingLine)
+                    if self.drawingLine.getPt(0)[0] == self.drawingLine.getPt(1)[0]:
+                        self.sketch.constraints.append(
+                                Vertical(self.drawingLine, 0,
+                                    self.drawingLine, 1))
+                    elif (self.drawingLine.getPt(0)[1]
+                            == self.drawingLine.getPt(1)[1]):
+                        self.sketch.constraints.append(
+                                Horizontal(self.drawingLine, 0,
+                                    self.drawingLine, 1))
+                    start = self.drawingLine.getPt(1)
+                self.drawingLine = Line(start[0], start[1], start[0], start[1])
+                self.queue_redraw()
         elif event.button == 2:
             self.panning = True
             self.panning_start = (event.x, self.size[1] - event.y)
         elif event.button == 3:
-            if self.drawingLine is not None:
-                # cancel line currently being drawn
-                self.drawingLine = None
-                self.queue_redraw()
+            if self.mode == 'line':
+                if self.drawingLine is not None:
+                    # cancel line currently being drawn
+                    self.drawingLine = None
+                    self.queue_redraw()
 
     def button_release_event(self, widget, event, data = None):
         if event.button == 2:
@@ -362,3 +365,11 @@ class SketchWidget:
             glVertex(pt[0] + self.line_width * 2, pt[1] - l/2)
             glEnd()
         glPopAttrib()
+
+    def set_mode(self, mode):
+        if mode != self.mode:
+            if self.mode == 'line':
+                self.drawingLine = None
+            elif self.mode == 'circle':
+                self.drawingCircle = None
+            self.mode = mode
diff --git a/Window.py b/Window.py
index 288daa0..a900e62 100644
--- a/Window.py
+++ b/Window.py
@@ -19,38 +19,38 @@ class Window:
 
         ss.solve()
 
-        sw = SketchWidget(ss, self.window)
+        self.sw = SketchWidget(ss, self.window)
 
         self.toolbar = gtk.Toolbar()
         self.toolbar.set_style(gtk.TOOLBAR_BOTH)
         ttb = gtk.ToggleToolButton()
+        self.mode_buttons[ttb] = 'select'
         ttb.set_label('Select')
         ttb.connect('toggled', self.mode_toggle_event)
         ttb.set_active(True)
         self.toolbar.insert(ttb, -1)
-        self.mode_buttons[ttb] = 'select'
         ttb = gtk.ToggleToolButton()
+        self.mode_buttons[ttb] = 'line'
         ttb.set_label('Line')
         ttb.connect('toggled', self.mode_toggle_event)
         self.toolbar.insert(ttb, -1)
-        self.mode_buttons[ttb] = 'line'
         ttb = gtk.ToggleToolButton()
+        self.mode_buttons[ttb] = 'circle'
         ttb.set_label('Circle')
         ttb.connect('toggled', self.mode_toggle_event)
         self.toolbar.insert(ttb, -1)
-        self.mode_buttons[ttb] = 'circle'
 
         self.statusbar = gtk.Statusbar()
 
         vbox = gtk.VBox()
         vbox.pack_start(self.toolbar, expand = False)
-        vbox.pack_start(sw.widget, expand = True)
+        vbox.pack_start(self.sw.widget, expand = True)
         vbox.pack_start(self.statusbar, expand = False)
 
         self.window.add(vbox)
         self.window.show_all()
 
-        sw.widget.grab_focus()
+        self.sw.widget.grab_focus()
 
     def main(self):
         gtk.main()
@@ -74,4 +74,5 @@ class Window:
             for b in self.mode_buttons:
                 if b != ttb:
                     b.set_active(False)
+            self.sw.set_mode(self.mode_buttons[ttb])
         return True