.academy-background {
    position: fixed;
    inset: 0;
    z-index: -1;

    /* Gradient đỏ → nhạt */
    background: linear-gradient(
            to bottom,
            #e53935 0%,
            #e57373 40%,
            #f3c4c4 75%,
            #f5d6d6 100%
    );
}