.ribbon {
    width: 150px;
    height: 150px;
    overflow: hidden;
    position: absolute;
    top: -10px;
    right: -10px;
}

    .ribbon span {
        position: absolute;
        display: block;
        width: 225px;
        padding: 10px 0;
        background-color: #e74c3c;
        color: #fff;
        text-align: center;
        font-weight: bold;
        transform: rotate(45deg);
        top: 30px;
        right: -50px;
        box-shadow: 0 3px 10px -5px rgba(0, 0, 0, 1);
    }

.modal-dialog {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh; /* Full viewport height */
}