adding sphere to my code

hey there , I am trying to add a moving sphere to my code , i have created a simple stairway using cubes , now I want to add a sphere that moves from up to down, i don’t need special physics or etc,so it’s ok if it is simple, here is my code :

#include <GL/glut.h>

void init()
{
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_COLOR_MATERIAL);
}

void display()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    GLint viewport[4];
    glGetIntegerv(GL_VIEWPORT, viewport);
    double aspect = (double)viewport[2] / (double)viewport[3];
    gluPerspective(60, aspect, 1, 100);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    // move back a bit
    glTranslatef( 0, 0, -35 );

    static float angle = 0;
    angle += 1.0f;

    glPushMatrix();
        glTranslatef(0,0,0);
        glRotatef(angle, 0.1, 0.2, 0.5);
        glColor3ub(255,0,255);
        glutSolidCube(5);
    glPopMatrix();

    glPushMatrix();
        glTranslatef(3,3,3);
        glRotatef(angle, 0.1, 0.2, 0.5);
        glColor3ub(255,0,0);
        glutSolidCube(5);
    glPopMatrix();

    glPushMatrix();
        glTranslatef(6,6,6);
        glRotatef(angle, 0.1, 0.2, 0.5);
        glColor3ub(0,255,0);
        glutSolidCube(5);
    glPopMatrix();

    glPushMatrix();
        glTranslatef(-3,-3,-3);
        glRotatef(angle, 0.1, 0.2, 0.5);
        glColor3ub(0,0,255);
        glutSolidCube(5);
    glPopMatrix();

    glPushMatrix();
        glTranslatef(-6,-6,-6);
        glRotatef(angle, 0.1, 0.2, 0.5);
        glColor3ub(255,255,0);
        glutSolidCube(5);
    glPopMatrix();

    glutSwapBuffers();
}

void reshape(int w, int h)
{
    glViewport(0, 0, w, h);
}

void timer(int extra)
{
    glutPostRedisplay();
    glutTimerFunc(16, timer, 0);
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitWindowSize(640,480);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
    glutCreateWindow("CUBES");

    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutTimerFunc(0, timer, 0);

    init();

    glutMainLoop();
    return 0;
}

thanks a lot.

See glusphere for an easy way to draw a sphere.