diff -r ad291f7e297d Lib/turtledemo/__main__.py
--- a/Lib/turtledemo/__main__.py	Mon Jul 28 00:18:43 2014 +0200
+++ b/Lib/turtledemo/__main__.py	Sun Jul 27 19:43:31 2014 -0700
@@ -12,6 +12,7 @@
 import time
 
 demo_dir = os.path.dirname(os.path.abspath(__file__))
+darwin = sys.platform == 'darwin'
 
 STARTUP = 1
 READY = 2
@@ -21,7 +22,9 @@
 
 menufont = ("Arial", 12, NORMAL)
 btnfont = ("Arial", 12, 'bold')
-txtfont = ('Lucida Console', 8, 'normal')
+txtfont = ['Lucida Console', 8, 'normal']
+
+MINIMUM_FONT_SIZE = 8
 
 def getExampleEntries():
     return [entry[:-3] for entry in os.listdir(demo_dir) if
@@ -102,7 +105,7 @@
         hbar['command'] = text.xview
         hbar.pack(side=BOTTOM, fill=X)
 
-        text['font'] = txtfont
+        text['font'] = tuple(txtfont)
         text['yscrollcommand'] = vbar.set
         text['xscrollcommand'] = hbar.set
         text.pack(side=LEFT, fill=BOTH, expand=1)
@@ -115,7 +118,7 @@
         turtle._Screen._canvas = self._canvas = canvas = turtle.ScrolledCanvas(
                 root, 800, 600, self.canvwidth, self.canvheight)
         canvas.adjustScrolls()
-        canvas._rootwindow.bind('<Configure>', self.onResize)
+        self._makeBindings(canvas._rootwindow)
         canvas._canvas['borderwidth'] = 0
 
         self.screen = _s_ = turtle.Screen()
@@ -124,6 +127,27 @@
         turtle.RawTurtle.screens = [_s_]
         return canvas
 
+    def _makeBindings(self, widget):
+        shortcut = 'Command' if darwin else 'Control'
+        widget.bind('<Configure>', self.onResize)
+        widget.bind_all('<%s-minus>' % shortcut, self._decreaseFont)
+        widget.bind_all('<%s-equal>' % shortcut, self._increaseFont)
+        widget.bind_all('<%s-plus>' % shortcut, self._increaseFont)
+        widget.bind_all('<Control-MouseWheel>', self._updateFont)
+
+    def _updateFont(self, event):
+        txtfont[1] = max(txtfont[1] + event.delta // (-1 if darwin else 120),
+                            MINIMUM_FONT_SIZE)
+        self.text['font'] = tuple(txtfont)
+
+    def _decreaseFont(self, dummy):
+        txtfont[1] = max(txtfont[1] - 1, MINIMUM_FONT_SIZE)
+        self.text['font'] = tuple(txtfont)
+
+    def _increaseFont(self, dummy):
+        txtfont[1] += 1
+        self.text['font'] = tuple(txtfont)
+
     def configGUI(self, menu, start, stop, clear, txt="", color="blue"):
         self.ExamplesBtn.config(state=menu)