#include <GL\glut.h>
#include <math.h>
GLfloat v=0;
GLfloat xc=0.5;
GLfloat yc=0.5;
void Square3f(GLfloat  x, GLfloat  y, GLfloat size){
  glBegin(GL_POLYGON);
      glVertex3f(x, y, 0);
      glVertex3f(x, y+size,0);
      glVertex3f(x+size,y+size,0);
      glVertex3f(x+size, y,0);
  glEnd();
}

void Grid(int  n, GLfloat size){
  int i;
  int j;
  GLfloat  x=0,y=0;
  bool f=true,start=false;
       glColor3f(0.5,0.5,0.5);
  for(i=0;i<n;i++){
    x=i*size;
    f=start;
    for(j=0;j<n;j++){
      y=j*size;
      if(f==true) {
        glColor3f(0.5,0.5,0.5);
        f=false;
      }else{
        glColor3f(0.3,0.7,0.7);
        f=true;
      }
      Square3f(x,y,size);
    }
     start=!start;
  }
}
void simple(){
    

	glBegin(GL_POLYGON);
		glColor3f(0.0,0.0,0.0);
		glVertex3f(-0.5,-0.5,-3.0);
		glColor3f(1.0,0.0,0.0);
		glVertex3f(0.5,-0.5,-3.0);
		glColor3f(0.0,0.0,1.0);
		glVertex3f(0.5,0.5,-3.0);
	glEnd();
}

void Display(void)
{
 
	
   glClear (GL_COLOR_BUFFER_BIT);
   glColor3f (1.0, 1.0, 1.0);
   glLoadIdentity ();             /* clear the matrix */
   gluLookAt (0.0,v, sqrt(v*v-0.5*0.5), 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
   glScalef (1.0, 2.0, 1.0);      /* modeling transformation */ 
   Grid(5,0.5 );
   glTranslatef(xc, yc, 0.0);
   glColor3f (1.0, 1.0, 0.0);
   glutSolidCube(0.2);
   glFlush ();
}

void Reshape(int w, int h)
{
 
   glViewport (0, 0, (GLsizei) w, (GLsizei) h); 
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   glFrustum (-1.0, 1.0, (GLfloat)(-1)*w/h, 1.0, 1.5, 20.0);
   glMatrixMode (GL_MODELVIEW);
}


void Keyboard(unsigned char key, int x, int y)
//Note: because there is an Idle-func, we don't have to call Display here
{	
	switch(key)
	{
	case 'q':	//ESC
		exit(0);
		break;
	case 'a':		//a
	    v+=0.1;
		break;
	case 'z':		//d
	    v-=0.1;
        break;
 	case 'e':		//a
	    yc+=0.1;
		break;
	case 'd':		//d
	    yc-=0.1;
        break;
 	case 's':		//a
	    xc-=0.1;
		break;
	case 'f':		//d
	    xc+=0.1;
        break;


	}
	Display();
}


void init(void){
  glClearColor(0.0,0.0,0.0,1.0);
  glEnable(GL_CULL_FACE);
  glCullFace(GL_FRONT);
  glPolygonMode(GL_FRONT_AND_BACK , GL_FILL);
}

int main (int argc, char **argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB|GLUT_DEPTH);
	glutInitWindowSize(700,700);
	glutCreateWindow("Demo"); 
    init();
	glutDisplayFunc(Display);
	glutReshapeFunc(Reshape);
    glutKeyboardFunc (Keyboard);
	glutMainLoop();
	return 0;
}