Do text substitution on main page

docs/index.html

@@ -23,18 +23,38 @@
 
 <div id="masthead">
     <!-- START: /masthead-incl.html -->
-    <script>$("#masthead").load("/masthead-incl.html");</script>
+<!--<div class="masthead-title" style="background-image: url('images/screenshot-mainwin.png');">-->
+<div class="masthead-title">
+    6502bench
+</div>
     <!-- END: /masthead-incl.html -->
 </div>
 
 <div id="topnav">
     <!-- START: /topnav-incl.html active:#topnav-home -->
-    <script>
-        // Load global topnav content, and mark current page active.
-        $("#topnav").load("/topnav-incl.html", function() {
-            $("#topnav-home").addClass("active")
-        });
-    </script>
+<!-- top navigation bar contents -->
+<nav>
+    <a id="topnav-home" class="active" href="/">HOME</a>
+    <a id="topnav-sgtutorial" href="/sgtutorial">SourceGen Tutorial</a>
+    <a id="topnav-menuicon" href="javascript:void(0);" class="icon" onclick="toggleSidenav()">
+        <i class="fa fa-bars"></i>
+    </a>
+</nav>
+<script>
+    // If page has no sidenav, don't show the sidenav toggle button.
+    if (document.getElementById("sidenav") == undefined) {
+        $("#topnav-menuicon").hide();
+    }
+
+    // Sidenav toggle function.
+    //
+    // Use a jQuery function to toggle the sidenav bar.  The initial state
+    // is undefined / inherited, so it will pop in and out as the screen
+    // resizes around the "large" breakpoint.
+    function toggleSidenav() {
+        $("#sidenav").toggle("fast");
+    }
+</script>
     <!-- END: /topnav-incl.html -->
 </div>
 
@@ -172,7 +192,15 @@ The full source code is available on
 
 <div id="footer">
     <!-- START: /footer-incl.html -->
-    <script>$("#footer").load("/footer-incl.html");</script>
+<hr/>
+<p>Copyright 2021 faddenSoft</p>
+<!-- <p id="screen-size"></p>
+<script>
+    var w = window.innerWidth;
+    var h = window.innerHeight;
+    var x = document.getElementById("screen-size");
+    x.innerHTML = "DEBUG: initial window size " + w + "x" + h;
+</script> -->
     <!-- END: /footer-incl.html -->
 </div>