code: public final void setScreenSize(int screenWidth, int screenHeight)
      {
          this.screenWidth = screenWidth;
          this.screenHeight = screenHeight;
          final int w = (int) Math.ceil(screenWidth / (surface.getWidth() * 0.6 * factH)) + 1;
          amplitude = (int) Math.ceil(w / 2.0) + 1;
      }
docs: Set the screen size. Used to know the parallax amplitude, and the overall surface to render in order to fill the
  screen.
  
  @param screenWidth The screen width.
  @param screenHeight The screen height.