diff --git a/grid-n-view.html b/grid-n-view.html
index eda8f5f..14a7c13 100644
--- a/grid-n-view.html
+++ b/grid-n-view.html
@@ -48,7 +48,7 @@
 - Gallery: remove image
 - <b>Gallery: serialize / deserialize</b>
 - <s>Lightbox: navigation (keyboard / mouse)</s>
-- Lightbox: fullscreen mode
+- <s>Lightbox: fullscreen mode</s>
 - Gallery: element (???)
 - ...
 </pre>
diff --git a/grid-n-view.js b/grid-n-view.js
index 6331608..d179943 100644
--- a/grid-n-view.js
+++ b/grid-n-view.js
@@ -647,8 +647,9 @@ var Lightbox = {
 		this.dom.querySelector('.fullscreen')
 			.addEventListener('click', function(evt){
 				evt.stopPropagation()
-				// XXX
-			})
+				document.fullscreenElement ?
+					document.exitFullscreen()
+					: that.dom.requestFullscreen() })
 		// click...
 		var deadzone = this.navigation_deadzone ?? 100
 		this.dom