Instead of creating an `event` variable here, since it's not really always an event, just use `originalEvent` for the `.button` check below and do the `isTouch ? event.changedTouches[ 0 ] : event` right when calling `getMouseRelative`. This way we don't have this `event` variable that might be an event or might be a touch point.

Of course if you do that, you can rename `originalEvent` to `event` if you want to.