Add a fullscreen button

xray.html

@@ -33,6 +33,7 @@
             <input type="number" id="softness-input" placeholder="25" value="25">
             <input type="range" id="softness-slider" min="0" max="100" value="25">
         </label>
+        <button id="fullscreen-button">Fullscreen</button>
     </div>
     
     <div id="fill-div">

xray.js

@@ -213,6 +213,20 @@ document.addEventListener("DOMContentLoaded", e => {
         }
     })
     
+    document.querySelector("#fullscreen-button").addEventListener("click", function toggleFullScreen() {
+        var doc = window.document;
+        var docEl = doc.documentElement;
+    
+        var requestFullScreen = docEl.requestFullscreen || docEl.mozRequestFullScreen || docEl.webkitRequestFullScreen || docEl.msRequestFullscreen;
+        var cancelFullScreen = doc.exitFullscreen || doc.mozCancelFullScreen || doc.webkitExitFullscreen || doc.msExitFullscreen;
+    
+        if (!doc.fullscreenElement && !doc.mozFullScreenElement && !doc.webkitFullscreenElement && !doc.msFullscreenElement) {
+            requestFullScreen.call(docEl);
+        }
+        else {
+            cancelFullScreen.call(doc);
+        }
+    });
 });
 
 function load() {