#mrt-container {
    container-name: mrtContainer;
}

@container mrtContainer (inline-size < 600px) {
    #mrt-container .text-1 {
        font-size: 12px;
        color: red;
    }
    #mrt-container .text-2 {
        font-size: 99px;
    }
    #mrt-container .text-3 {
        font-size: 25px;
    }
    #mrt-container .text-4 {
        font-size: 45px;
    }
}

#mrt-container .text-1 {
    font-size: 10px;
}
#mrt-container .text-2 {
    font-size: 12px;
}
#mrt-container .text-3 {
    font-size: 15px;
}
#mrt-container .text-4 {
    font-size: 25px;
}