finalize simple game

exercise-07/index.html

@@ -9,6 +9,7 @@
         <script src="https://code.jquery.com/jquery-3.1.1.min.js" integrity="sha256-hVVnYaiADRTO2PzUGmuLJr8BLUSjGIZsDYGmIJLv2b8=" crossorigin="anonymous"></script>
         
         <script type="text/javascript">
+            /* global $ */
             function buttonClickHandler(event) {
                 alert("Clicked: " + event.target.textContent);
             }