OpenGL code for sun rise and down

This source code is for displaying the moving sun and mountains. The sun will rise from one side and down in other side.

OpenGL program:-

#include<iostream>
#include<stdlib.h>

#ifdef __APPLE__
#include<openGL/openGL.h>
#include<GLUT/glut.h>
#else 
#include<GL/glut.h>
#endif

using namespace std;

float ballX = -0.8f;
float ballY = -0.3f;
float ballZ = -1.2f;
float colR=3.0;
float colG=1.5;
float colB=1.0;
float bgColR=0.0;
float bgColG=0.0;
float bgColB=0.0;

static int flag=1;

void drawBall(void) {

        glColor3f(colR,colG,colB); //set ball colour
        glTranslatef(ballX,ballY,ballZ); //moving it toward the screen a bit on creation
        glutSolidSphere (0.05, 30, 30); //create ball.

}

void drawAv(void) {

        glBegin(GL_POLYGON);
        
        glColor3f(1.0,1.0,1.0);
   
        glVertex3f(-0.9,-0.7,-1.0);

        glVertex3f(-0.5,-0.1,-1.0);

        glVertex3f(-0.2,-1.0,-1.0);

        glVertex3f(0.5,0.0,-1.0);

        glVertex3f(0.6,-0.2,-1.0);

        glVertex3f(0.9,-0.7,-1.0);

    glEnd();

}

void drawClouds(){}

void keyPress(int key, int x, int y)
{
      if(key==GLUT_KEY_RIGHT)
        ballX -= 0.05f;
    if(key==GLUT_KEY_LEFT)
        ballX  += 0.05f;

    glutPostRedisplay();
}

void initRendering() {
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_COLOR_MATERIAL);
    glEnable(GL_LIGHTING); //Enable lighting
    glEnable(GL_LIGHT0); //Enable light #0
    glEnable(GL_LIGHT1); //Enable light #1
    glEnable(GL_NORMALIZE); //Automatically normalize normals
    //glShadeModel(GL_SMOOTH); //Enable smooth shading
}

//Called when the window is resized
void handleResize(int w, int h) {
    //Tell OpenGL how to convert from coordinates to pixel values
    glViewport(0, 0, w, h);
    
    glMatrixMode(GL_PROJECTION); //Switch to setting the camera perspective
    
    //Set the camera perspective
    glLoadIdentity(); //Reset the camera
    gluPerspective(45.0,                  //The camera angle
                   (double)w / (double)h, //The width-to-height ratio
                   1.0,                   //The near z clipping coordinate
                   200.0);                //The far z clipping coordinate
}

void drawScene()
{
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    glClearColor(bgColR,bgColG,bgColB,0.0);
    glMatrixMode(GL_MODELVIEW);
   
    glLoadIdentity();
   
    //Add ambient light
    GLfloat ambientColor[] = {0.2f, 0.2f, 0.2f, 1.0f}; //Color (0.2, 0.2, 0.2)
    glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientColor);
   
    //Add positioned light
    GLfloat lightColor0[] = {0.5f, 0.5f, 0.5f, 1.0f}; //Color (0.5, 0.5, 0.5)
    GLfloat lightPos0[] = {4.0f, 0.0f, 8.0f, 1.0f}; //Positioned at (4, 0, 8)
    glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0);
    glLightfv(GL_LIGHT0, GL_POSITION, lightPos0);
   
    //Add directed light
    GLfloat lightColor1[] = {0.5f, 0.2f, 0.2f, 1.0f}; //Color (0.5, 0.2, 0.2)
    //Coming from the direction (-1, 0.5, 0.5)
    GLfloat lightPos1[] = {-1.0f, 0.5f, 0.5f, 0.0f};
    glLightfv(GL_LIGHT1, GL_DIFFUSE, lightColor1);
    glLightfv(GL_LIGHT1, GL_POSITION, lightPos1);

    //drawing the SUN
    glPushMatrix();
        drawBall();
    glPopMatrix();
    //drawing the Mount Avarest
    glPushMatrix();
        drawAv();
    glPopMatrix();

    //drawing the Clouds
    glPushMatrix();
        drawClouds();
    glPopMatrix();

    glutSwapBuffers();
}

//float _angle = 30.0f;
void update(int value) {
   
    if(ballX>0.9f)
    {
        ballX = -0.8f;
        ballY = -0.3f;
        flag=1;
        colR=2.0;
        colG=1.50;
        colB=1.0;

        bgColB=0.0;
    }
   
    if(flag)
    {
    ballX += 0.001f;
    ballY +=0.0007f;
    colR-=0.001;
    //colG+=0.002;
    colB+=0.005;

    bgColB+=0.001;

       if(ballX>0.01)
       {
           flag=0;

       }
    }
    if (!flag)
    {
        ballX += 0.001f;
        ballY -=0.0007f;
        colR+=0.001;
        colB-=0.01;

        bgColB-=0.001;

        if(ballX<-0.3)
       {
           flag=1;

       }
    }
   
    glutPostRedisplay(); //Tell GLUT that the display has changed
   
    //Tell GLUT to call update again in 25 milliseconds
    glutTimerFunc(25, update, 0);
}

int main(int argc,char** argv)
{
    glutInit(&argc,argv);
   
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);
   
    glutInitWindowSize(400,400);
   
    glutCreateWindow("Sun");
   
    initRendering();
   
    glutDisplayFunc(drawScene);

    glutFullScreen();
   
    glutSpecialFunc(keyPress);
    glutReshapeFunc(handleResize);

    glutTimerFunc(25, update, 0);

    glutMainLoop();
   
    return(0);
}