docs: public float getRotation() {
      if (mDetector.getPointerCount() < 2) {
        return 0;
      } else {
        float startDeltaX = mDetector.getStartX()[1] - mDetector.getStartX()[0];
        float startDeltaY = mDetector.getStartY()[1] - mDetector.getStartY()[0];
        float currentDeltaX = mDetector.getCurrentX()[1] - mDetector.getCurrentX()[0];
        float currentDeltaY = mDetector.getCurrentY()[1] - mDetector.getCurrentY()[0];
        float startAngle = (float) Math.atan2(startDeltaY, startDeltaX);
        float currentAngle = (float) Math.atan2(currentDeltaY, currentDeltaX);
        return currentAngle - startAngle;
      }
    }