#include <glut.h>

void display() {
 glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0,0.2,0.2);
 glBegin(GL_POLYGON);
  glVertex2f(-0.5,-0.5);
  glVertex2f(0.5,0.5);
  glVertex2f(-0.5,0.5);
  glVertex2f(0.5,-0.5);
 glEnd();
 glFlush();
 }

int main(int argc,char *argv[]) {
 glutInit(&argc,argv);
 glutCreateWindow("simple");
 glutDisplayFunc(display);
 glutMainLoop();
 }