add swipe gesture support

js/keyboard_input_manager.js

@@ -47,6 +47,23 @@ KeyboardInputManager.prototype.listen = function () {
 
   var retry = document.getElementsByClassName("retry-button")[0];
   retry.addEventListener("click", this.restart.bind(this));
+
+  // Listen to swipe events
+  var gestures = [Hammer.DIRECTION_UP, Hammer.DIRECTION_RIGHT,
+                  Hammer.DIRECTION_DOWN, Hammer.DIRECTION_LEFT];
+
+  var gameContainer = document.getElementsByClassName("game-container")[0];
+  var handler       = Hammer(gameContainer, {
+    drag_block_horizontal: true,
+    drag_block_vertical: true
+  });
+  
+  handler.on("swipe", function (event) {
+    event.gesture.preventDefault();
+    mapped = gestures.indexOf(event.gesture.direction);
+
+    if (mapped !== -1) self.emit("move", mapped);
+  });
 };
 
 KeyboardInputManager.prototype.restart = function (event) {