glClear( GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT );

  glMatrixMode(gl_modelview);
  glLoadIdentity;
  glMatrixMode(gl_projection);
  glLoadIdentity;
  glOrtho(0, Screen_width, 0, Screen_height, 1, 100);
  //BackgroundRender.Bind;
  //BackgroundRender.UniformFloat['height']:= 0.0;
  glColor3f(1.0, 1.0, 1.0);
  glBegin(gl_quads);
    glVertex2f(0, 0);
    glVertex2f(screen_width, 0);
    glVertex2f(screen_width, screen_height);
    glVertex2f(0, screen_height);
  glEnd;
  //BackgroundRender.UnBind;
  glLoadIdentity;
  gluPerspective(45, screen_width / screen_height, 1, 100);

  glMatrixMode(gl_modelview);
  glLoadIdentity;
  glTranslatef( 0.0, -10.0, -25.0 );
  glRotatef(40, 1, 0, 0);
  glScalef(-1, -1, -1);

  render;

  updateGame;

  // Buffer-Wechseln ==> Anzeigen
  SDL_GL_SwapBuffers;