Fix: () => { } -> function() { }

src/game/lib/button/fullscreen_button.js

@@ -29,13 +29,13 @@ class FullscreenButton extends RoundRectButton {
 		super(
 			setting,
 			RoundRectButton.NONE_ICON, RoundRectButton.NONE_BUTTON_TEXT,
-			() => {
+			(function() {
 				if(game.scale.isFullScreen) {
 					game.scale.stopFullScreen();
 				} else {
 					game.scale.startFullScreen();
 				}
-			}
+			})
 		);
 
 		let icon_fullscreen = game.add.sprite(0, 0, 'icon_fullscreen');