Add menu separators for external and icon links; update SolidificationFront2D tutorial with blog reference

Author: nikoscham

FEAScript-website.css

@@ -151,14 +151,16 @@ mjx-container {
   color: #333;
 }
 
-/* Menu separator */
-.menu-separator {
-  color: #ccc;
-  margin: 0 5px;
-  font-weight: 300;
-  display: inline-block;
-  vertical-align: middle;
-  line-height: normal;
+/* Add a separator before external links */
+#menu li.external-link-start {
+  padding-left: 1em;
+  border-left: 2px solid #999;
+}
+
+/* Add a space before icon links */
+#menu li.icon-link-start {
+  /* margin-left: 1em; */
+  padding-left: 1em;
 }
 
 /* Loading spinner */

index.html

@@ -75,37 +75,37 @@ <h1>A JavaScript Finite Element Simulation Library</h1>
 
     <ul id="menu">
       <li><a href="#gettingstarted">Getting Started</a></li>
-      <li>&#x2022;</li>
       <li><a href="#features">Features</a></li>
-      <li>&#x2022;</li>
       <li><a href="#tutorials">Tutorials</a></li>
-      <li>&#x2022;</li>
       <li><a href="#documentation">Documentation</a></li>
-      <li>&#x2022;</li>
       <li><a href="#licensing">Licensing</a></li>
-      <li class="menu-separator">|</li>
-      <li>
-        <a href="https://platform.feascript.com/"> FEAScript platform 🧩 </a>
+      <li class="external-link-start">
+        <a href="https://platform.feascript.com/"> FEAScript platform</a>
       </li>
-      <li>&#x2022;</li>
-      <li>
-        <a href="https://blog.feascript.com/">
-          FEAScript blog
+      <li class="icon-link-start">
+        <a href="https://blog.feascript.com/" title="FEAScript Blog">
           <img
-            src="https://upload.wikimedia.org/wikipedia/commons/4/43/Feed-icon.svg"
+            src="https://upload.wikimedia.org/wikipedia/commons/8/89/Font_Awesome_5_brands_blogger.svg"
             alt="Blog Icon"
-            style="width: 13px; height: 13px; vertical-align: middle; margin-left: 2px; margin-bottom: 4px"
+            style="height: 18px; vertical-align: middle"
+          />
+        </a>
+      </li>
+      <li>
+        <a href="https://www.youtube.com/@FEAScript" title="FEAScript YouTube">
+          <img
+            src="https://upload.wikimedia.org/wikipedia/commons/8/8b/YouTube_dark_icon_%282017%29.svg"
+            alt="YouTube Icon"
+            style="height: 16px; vertical-align: middle"
           />
         </a>
       </li>
-      <li>&#x2022;</li>
       <li>
-        <a href="https://github.com/FEAScript/FEAScript-core">
-          GitHub
+        <a href="https://github.com/FEAScript/FEAScript-core" title="FEAScript GitHub">
           <img
-            src="https://github.githubassets.com/images/modules/logos_page/GitHub-Mark.png"
-            alt="GitHub Logo"
-            style="width: 18px; height: 18px; vertical-align: middle; margin-left: 2px; margin-bottom: 4px"
+            src="https://upload.wikimedia.org/wikipedia/commons/9/91/Octicons-mark-github.svg"
+            alt="GitHub Icon"
+            style="height: 18px; vertical-align: middle"
           />
         </a>
       </li>

tutorials/SolidificationFront2D.html

@@ -98,7 +98,9 @@ <h2 id="mathematicalformulation"><a name="Mathematical formulation"></a>Mathemat
       m/s throughout the domain, which reduces the equation to: \(|\nabla \phi(x,y)| = 1\). It's worth noting,
       however, that actual solidification speeds in real materials typically range from micrometers per second
       to centimeters per second for most metals and alloys. Only specialized rapid solidification processes
-      might achieve speeds approaching or exceeding 1 m/s.
+      might achieve speeds approaching or exceeding 1 m/s. For more detailed background on the eikonal
+      equation and its mathematical properties, please see our
+      <a href="https://blog.feascript.com/tutorial/2025/06/15/eikonal-equation.html">blog post</a>.
     </p>
     <img src="../assets/SolidificationFront2D.png" width="300" />
     <p>