double Timestamp() // seconds
{
    const double scale = 1.0 / 1000.0;
    return SDL_GetTicks() * scale;
}

    int frames = 0;

    const double dt = 0.01;

    double lastFPS = Timestamp();
    double currentTime = Timestamp();
    double timeAccum = 0.0;

    double t = 0.0;

    while (1)
    {
        double newTime = Timestamp();
        double frameTime = newTime - currentTime;
        if (frameTime > MAX_UPDATE_TIME)
            frameTime = MAX_UPDATE_TIME; // avoid runaway simulation
        currentTime = newTime;

        timeAccum += frameTime;

        while (timeAccum >= dt)
        {
            // simulate physics

            timeAccum -= dt;
            t += dt;
        }



    blah blah blah

        glFlush();
        SDL_GL_SwapBuffers();

        frames++;

        if (currentTime - lastFPS > 1.0) {
            std::cout << "FPS: "
                << frames / (currentTime - lastFPS)
                << std::endl;
            lastFPS = currentTime;
            frames = 0;
        }
}