:root {
    --modal-duration: .5s;
}
.modal {
    display: none;
    position: fixed;
    z-index: 1;
    left:0;
    top:0;
    height: 100%;
    width: 100%;
    overflow: auto;
    background: rgba(0, 0, 0, .5)
}

.modal-content {
    background: #fff;
    text-align:center;
    margin: 10% auto;
    width: 350px;
    border-radius: 10px;
    padding: 3rem;
    box-shadow: 0 5px 8px rgba(0, 0, 0, .2), 0 7px 20px rgba(0, 0, 0, .17);
    animation-name: modalopen;
    animation-duration: var(--modal-duration);
}

.modal-content h1 {
    margin-bottom: 1rem;
}

.modal-content p {
    font-size: 1.2rem;
    margin-top: 1rem;
}

@keyframes modalopen {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}