Ensure the Try Again button actually disappears when selected in Internet Explorer

js/html_actuator.js

@@ -114,5 +114,7 @@ HTMLActuator.prototype.message = function (won) {
 };
 
 HTMLActuator.prototype.clearMessage = function () {
-  this.messageContainer.classList.remove("game-won", "game-over");
+  // IE only takes one value to remove at a time.
+  this.messageContainer.classList.remove("game-won");
+  this.messageContainer.classList.remove("game-over");
 };