Makes sliding and merging work.

index.html

@@ -34,7 +34,10 @@ td.visible {
   <button id="btnDown" onclick="btnDown_onClick()">Down</button>
   <button id="btnRight" onclick="btnRight_onClick()">Right</button>
   </section>
-  <button onclick="btnGo_onClick();" id="btnGo">Go</button>
+  <section>
+    <button id="btnStart" onclick="btnStart_onClick();">Start</button>
+    <button id="btnRedraw" onclick="btnRedraw_onClick();">Redraw</button>  
+  </section>
   <script src="main.js"></script>
 </body>
 </html>