code: @Override
      public final void update(double extrp, double speed, double y)
      {
          final int lowest = totalHeight;
          int py;
          if (maxY == 0)
          {
              py = (int) y;
          }
          else
          {
              final double currentY = UtilMath.clamp(y, minY, maxY);
              py = (int) (currentY / maxY * lowest) - lowest + offsetY;
              if (py > 0)
              {
                  py = 0;
              }
          }
  
          for (final BackgroundComponent component : components)
          {
              component.update(extrp, 0, py, speed);
          }
      }
docs: /*
  Background