Open http://kaijukun.com/lab/webgl/duel
and attach two gamepads to your OS.
The controls are analog stick and A for shooting
On Windows:
Chrome had correct controls but it needed time(about minute) for controls to work
Firefox had terrible axis mapping(for example, trying to move upwards most often resolved into southwest or southeast movement). Button worked correctly
On Mac:
The gamepads didn't work on Chrome at all no matter the attempts.