The Gamepad Button Down Event.
This event is dispatched by a Gamepad instance when a button has been pressed on it.
Listen to this event from a Gamepad instance. Once way to get this is from the
pad2, etc properties on the Gamepad Plugin:
Note that you will not receive any Gamepad button events until the browser considers the Gamepad as being 'connected'.
You can also listen for a DOWN event from the Gamepad Plugin. See the
BUTTON_DOWN event for details.
The index of the button that was pressed.
The value of the button at the time it was pressed. Between 0 and 1. Some Gamepads have pressure-sensitive buttons.
A reference to the Button which was pressed.