.open {
    display: inline-block;
    cursor:pointer;
}

.open:hover {
    text-decoration: underline;
}

#popup {
    display: none;
}

.overlay {
    display: none;
}

#popup:checked + .overlay {
    display: block;
    position: fixed;
    width: 100%;
    top: 0;
    left: 0;
    z-index: 9999;
}

.window {
    position: fixed;
    top: 50%;
    left: 50%;
    width: 300px;
    padding: 50px;
    height: 150px;
    font-size: 16px;
    font-weight: normal;
    line-height: 30px;
    transform: translate(-50%, -50%);
    background-color: #fffacd;
}

.close {
    position: absolute;
    top: 4px;
    right: 4px;
    cursor:pointer;
}