//To change to color of anything, you must call a color function
//before the drawing of the object. to do this you can use
//glColor3f(R,G,B); or glColor4f(R,G,B,A); but in this tutorial
//we are only going to use glColor3f because glColor4f has an extra
//use which is known as alpha. Also known as transparency or opacity, in other words, how much you can see through it. 

//Now with R, G, B and A, the highest value you can have is a 1.
//The lower the number, the less of that color. 

//With: glColor3f(1.0, 0.0, 0.0); you can see that we have set
//the R value to 1, and all the other values to 0. This means that it will only show the color red, and to its full extent. 

#include <GL/gl.h>
#include <GL/glut.h>

void square (void) {
	glColor3f(1.0, 0.0, 0.0); //this will set the square to red.
	glBegin(GL_QUADS);
	glVertex3f(-0.5, -0.5, 0.0);
	glVertex3f(-0.5, 0.5, 0.0);
	glVertex3f(0.5, 0.5, 0.0);
	glVertex3f(0.5, -0.5, 0.0);
	glEnd();
}

void display (void) {
	glClearColor (0.0,0.0,0.0,1.0);
    glClear (GL_COLOR_BUFFER_BIT);
    glLoadIdentity();  
    gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
	square();
	glFlush();
}

void reshape (int w, int h) {
	glViewport (0, 0, (GLsizei)w, (GLsizei)h);
	glMatrixMode (GL_PROJECTION);
	glLoadIdentity ();
	gluPerspective (60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
	glMatrixMode (GL_MODELVIEW);
}

int main (int argc, char **argv) {
    glutInit (&argc, argv);
	glutInitDisplayMode (GLUT_SINGLE);
	glutInitWindowSize (500, 500);
	glutInitWindowPosition (100, 100);
    glutCreateWindow ("A basic OpenGL Window");
    glutDisplayFunc (display);
	glutReshapeFunc (reshape);
    glutMainLoop ();
    return 0;
}