#include <GL/glut.h>

void display(void)
{
  glClear(GL_COLOR_BUFFER_BIT);
  glBegin(GL_LINE_LOOP);
  glColor3d(1.0, 0.0, 0.0);
  glVertex2d(-0.7, -0.7);
  glVertex2d(0.7, -0.7);
  glVertex2d(0.0, 0.7);
  glEnd();
}

void keyboard(unsigned char key, int x, int y)
{
  if (key == '\033') exit(0);  /* '\033' は ESC の ASCII コード */
}

int main(int argc, char *argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGBA);
  glutCreateWindow(argv[0]);
  glClearColor(1.0, 1.0, 1.0, 0.0);
  glutDisplayFunc(display);
  glutKeyboardFunc(keyboard);
  glutMainLoop();
  return 0;
}