GLint ct=1,arr[21]={10};
void display()
{
 int i;
 glClearColor(0.7f,0.0f,0.7f,1.0f);
 glClear(GL_COLOR_BUFFER_BIT);
 for(i=1;i<=10;i++){
  glColor4f(0.1f*i,0.1f*i,0.1f*i,1.0f);
  glBegin(GL_POLYGON);
   glVertex2i(arr[i],arr[i+10]);
   glVertex2i(arr[i],arr[i+10]-20);
   glVertex2i(arr[i]+20,arr[i+10]-20);
   glVertex2i(arr[i]+20,arr[i+10]);
   glEnd();
 }
 glFlush();
}
void Mouse(int button,int state,int x,int y)
{
 if(ct==11) ct=1;
 if(button==GLUT_LEFT_BUTTON && state ==GLUT_DOWN)
 {
  arr[ct]=x;
  arr[ct+10]=600-y;
  ct++;
 }
 glutPostRedisplay();
}
int main(int argc,char **argv)
{
 glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
 glOrtho(0,800,0,600,-1.0,1.0);
 glutInitWindowPosition(100,100);
 glutInitWindowSize(800,600);
 glutCreateWindow("sample");
 glutDisplayFunc(display);
 glutMouseFunc(Mouse);
 glutMainLoop();
}