@gama11 True! Took me a while to find out why things didn't work :P

HaxeFlixel offers FlxG.resizeWindow, it only works with desktop targets.

FYI, there's a tweet from HaxeFlixel for the 4.3.0 release.

@agustín-pérez-fernández Actually, it need not to.
As super.create() is just an empty function. I choose to remove it entirely.

The initial state has been changed to PlayState. However, you can easily change it in your Main.hx.

You may need to do a reinstall. It seems to fix the problem.
On the side, you can install Haxe latest builds which HaxeFlixel should work just well in.

Actually, the demo does use debug mode.

Check it again, it may be hidden

Optionally, refer to this: Build error caused by thumbs.db

Okay I just found an even better way after I stumbled upon the API of FlxG.keys:

FlxG.keys.preventDefaultKeys = [LEFT, RIGHT, UP, DOWN, SPACE];

Better way without modifying your index.html, put this in your Main.hx or anywhere in your Haxe code:

#if js
js.Browser.document.onkeydown = e -> e.preventDefault();
#end