function _handleStart(e) {
      if (_settings('touchEnabled')) {
        var x0,
            x1,
            y0,
            y1,
            pos0,
            pos1;

        _downTouches = e.touches;

        switch (_downTouches.length) {
          case 1:
            _camera.isMoving = true;
            _touchMode = 1;

            _startCameraX = _camera.x;
            _startCameraY = _camera.y;

            _lastCameraX = _camera.x;
            _lastCameraY = _camera.y;

            pos0 = position(_downTouches[0]);
            _startTouchX0 = pos0.x;
            _startTouchY0 = pos0.y;

            break;
          case 2:
            _camera.isMoving = true;
            _touchMode = 2;

            pos0 = position(_downTouches[0]);
            pos1 = position(_downTouches[1]);
            x0 = pos0.x;
            y0 = pos0.y;
            x1 = pos1.x;
            y1 = pos1.y;

            _lastCameraX = _camera.x;
            _lastCameraY = _camera.y;

            _startCameraAngle = _camera.angle;
            _startCameraRatio = _camera.ratio;

            _startCameraX = _camera.x;
            _startCameraY = _camera.y;

            _startTouchX0 = x0;
            _startTouchY0 = y0;
            _startTouchX1 = x1;
            _startTouchY1 = y1;

            _startTouchAngle = Math.atan2(
              _startTouchY1 - _startTouchY0,
              _startTouchX1 - _startTouchX0
            );
            _startTouchDistance = Math.sqrt(
              Math.pow(_startTouchY1 - _startTouchY0, 2) +
              Math.pow(_startTouchX1 - _startTouchX0, 2)
            );

            e.preventDefault();
            return false;
        }
      }
    }
The handler listening to the 'touchstart' event. It will set the touch
mode ("_touchMode") and start observing the user touch moves.

@param {event} e A touch event.