That's weird. We encountered no problems with X-Box gamepads (X-Box One gamepads to be specific). The only thing I can think of is making sure the gamepad is already connected, before launching the web-game. Can't say for sure if it will correctly detect the gamepad mid-game. Also while gamepads are supported, we did not have time to adapt the onscreen texts, e.g. "press space" labels and so on. For every menu where it says "space", A/LB/LT should work as well when using an X-Box controller.