# simple example taken from listing 1-1 (or 1-2) from OpenGL book
use OpenGL;
glpOpenWindow;
glClearColor(0,0,1,1);
glClear(GL_COLOR_BUFFER_BIT);
glOrtho(-1,1,-1,1,-1,1);
glColor3f(1,0,0);
glBegin(GL_POLYGON);
  glVertex2f(-0.5,-0.5);
  glVertex2f(-0.5, 0.5);
  glVertex2f( 0.5, 0.5);
  glVertex2f( 0.5,-0.5);
glEnd();
glpFlush();
print "Program 1-1 Simple, hit Enter in terminal window to quit:\n\n";
glpMainLoop;