Blow bubbles with C++

bubbles.cpp

void
blow_bubbles_till(bool& condition)
{
    static const char* sprite = ".     o     O     @     *";
    unsigned frame = 0;
    while (!condition) {
        boost::this_thread::sleep_for(boost::chrono::milliseconds(250));
        std::cerr << "\r‗‗" << std::string(sprite + frame * 5, 5) << ' ';
        frame = (frame + 1) % 5;
    }
    std::cerr << std::endl;
}