.modal {
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19), 0 6px 6px rgba(0, 0, 0, 0.23);
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.modal__overlay {
    background-color: rgba(0, 0, 0, 0.6);
}

@media screen and (max-width: 600px) {
    .modal {
        width: 90%;
    }
}