Feature: Portal system — entry points to other worlds (#5)

index.html

@@ -101,6 +101,32 @@
     <span>V</span> mode: <span id="nav-mode-label">WALK</span>
     <span id="nav-mode-hint" class="nav-mode-hint"></span>
   </div>
+
+  <!-- Portal Hint -->
+  <div id="portal-hint" class="portal-hint" style="display:none;">
+    <div class="portal-hint-key">F</div>
+    <div class="portal-hint-text">Enter <span id="portal-hint-name"></span></div>
+  </div>
+
+  <!-- Portal Activation Overlay -->
+  <div id="portal-overlay" class="portal-overlay" style="display:none;">
+    <div class="portal-overlay-content">
+      <div class="portal-overlay-header">
+        <div class="portal-overlay-status" id="portal-status-dot"></div>
+        <div class="portal-overlay-title" id="portal-overlay-title">PORTAL ACTIVATED</div>
+      </div>
+      <h2 id="portal-name-display">MORROWIND</h2>
+      <p id="portal-desc-display">The Vvardenfell harness. Ash storms and ancient mysteries.</p>
+      <div class="portal-redirect-box" id="portal-redirect-box">
+        <div class="portal-redirect-label">REDIRECTING IN</div>
+        <div class="portal-redirect-timer" id="portal-timer">5</div>
+      </div>
+      <div class="portal-error-box" id="portal-error-box" style="display:none;">
+        <div class="portal-error-msg">DESTINATION NOT YET LINKED</div>
+        <button id="portal-close-btn" class="portal-close-btn">CLOSE</button>
+      </div>
+    </div>
+  </div>
 </div>
 
 <!-- Click to Enter -->