Add listings

Listing_10.12.html

@@ -14,18 +14,23 @@
     <div class="container">
       <div class="content">
 
-  <h1>About</h1>
+  <h1>Sample Flask App</h1>
 
   <p>
-    This site is the final application in
+    This is the sample Flask app for
     <a href="https://www.learnenough.com/python-tutorial"><em>Learn Enough Python
-    to Be Dangerous</em></a>
-    by <a href="https://www.michaelhartl.com/">Michael Hartl</a>,
-    a tutorial introduction to the
-    <a href="https://www.python.org/">Python programming language</a> that
-    is part of
-    <a href="https://www.learnenough.com/">LearnEnough.com</a>.
+    to Be Dangerous</em></a>. Learn more on the <a href="/about">About</a> page.
   </p>
+
+  <p>
+    Click the <a href="https://en.wikipedia.org/wiki/Sator_Square">Sator
+    Square</a> below to run the custom <a href="/palindrome">Palindrome
+    Detector</a>.
+  </p>
+
+  <a class="sator-square" href="/palindrome">
+    <img src="/static/images/sator_square.jpg" alt="Sator Square">
+  </a>
       </div>
     </div>
   </body>