thing

void Application::loop() {
    using HRC = std::chrono::high_resolution_clock;
    using TimePoint = std::chrono::time_point<HRC>;
    using Nano = std::chrono::nanoseconds;
    using std::chrono::duration_cast;

    Nano sum{ Nano::zero() };
    TimePoint then{ HRC::now() };
    constexpr Nano ONE_SECOND{ 1000000000L };

    while (looping) {
        Nano timestep{ ONE_SECOND / tickrate };
        sum += duration_cast<Nano>(HRC::now() - then);
        then = HRC::now();

        //check for GameState swaps.
        if (gameStateQueue != nullptr && currentGameState != gameStateQueue) {
            currentGameState = gameStateQueue;
            currentGameState->init();
        }

        SDL_Event e{};
        while (SDL_PollEvent(&e)) {
            currentGameState->event_SDL(e);
        }

        while (sum >= timestep) {
            /* Temp start */
            static TimePoint lastTick{ HRC::now() };
            std::cout << "Time elapsed: " << duration_cast<Nano>(HRC::now() - lastTick).count() / 1000000000.0L << std::endl;
            lastTick = HRC::now();
            /* Temp end */
            currentGameState->tick();
            sum -= timestep;
        }

        currentGameState->render(static_cast<double>(sum.count()) / timestep.count());
    }
    currentGameState->shutdown();
    cleanup();
}