Implement 2D video controls for non-VR devices

- Add complete 2D control panel with HTML structure and CSS styling
- Implement JavaScript functionality for all control buttons:
  - Fullscreen toggle for immersive 16:9 video experience
  - Play/pause with dynamic icon switching
  - Back/forward 15-second skip controls
  - Mute/unmute toggle
  - Click-to-seek progress bar with real-time updates
- Add auto-hide behavior (5-second timeout) with mouse/touch activation
- Integrate with existing 2D mode - shows only when VR not supported
- Include all button PNG assets (normal and hover states)
- Responsive design for mobile devices
- Professional styling matching design specifications

index.html

@@ -31,8 +31,29 @@
 				<source src="sbs-video.mp4" type="video/mp4">
 			</video>
 			<button id="playBtn" aria-label="Play video">
-				<img src="play.png" alt="Play">
+				<img src="play.svg" alt="Play">
 			</button>
+			<div id="panel">
+				<div id="status">
+					<p id="video-title">Title</p>
+					<div id="progress">
+						<p id="current-time">00:00:00</p>
+						<div id="bar">
+							<div id="played"></div>
+						</div>
+						<p id="total-time">00:00:00</p>
+					</div>
+				</div>
+				<div id="controls">
+					<button id="fullscreen"></button>
+					<div id="nav">
+						<button id="back"></button>
+						<button id="play2"></button>
+						<button id="forward"></button>
+					</div>
+					<button id="mute"></button>
+				</div>
+			</div>
 		</div>
 	</main>
 	<script type="module" src="vr180-player.js"></script>