diff --git a/slides/introduction.html b/slides/introduction.html
index 820642c..d78cae2 100644
--- a/slides/introduction.html
+++ b/slides/introduction.html
@@ -3,6 +3,7 @@
 
 <head>
   <script src="highlight.js"></script>
+  <button id="toggle-highlights">Toggle Highlights</button>
   <style>
 	.highlight {
 		position: absolute;
