void draw()
{
    glClearColor(0.2, 0.2, 0.2, 0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // setup camera

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    gluPerspective(camera.fov, 1.33, 0.1, 1000);
    gluLookAt(0, 0, 0, 0, 0, -1, 0, 1, 0);


    // render world objects

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glRotatef(rad2deg(camera.roll), 0, 0, 1);
    glRotatef(rad2deg(camera.pitch), 1, 0, 0);
    glRotatef(rad2deg(camera.heading), 0, 1, 0);
    glTranslatef(-camera.pos.x, -camera.pos.y, -camera.pos.z);


    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);
    glEnable(GL_TEXTURE_2D);

    draw_checker();

    draw_maze();


    if (mflag) { genmap1(); mwall(); }


    static float t = 0;
    t += 2;
    glRotatef(t, 0, 1, 0);
    glTranslatef(0, 11, 0);


    draw_unit_cube();


    g_t += 0.001;

}