Tidied UI.

index.html

@@ -17,8 +17,10 @@
     <label>Expression to simplify:
       <input id="unsimplified" type="text" autocomplete="off" value="">
     </label>
+  </div>
+  <div>
     <label>Maximum number of operators:
-      <input id="operators" type="number" autocomplete="off" min="0" value="1">
+      <input id="operators" type="number" autocomplete="off" min="0" value="1" max="4">
     </label>
   </div>
   <div>