#mask {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 999;
    display: none;
    border-radius: 10px;
    transition: opacity 0.5s ease-in-out;
}

#popup {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: #fff;
    padding: 20px;
    z-index: 1000;
    display: none;
    border-radius: 10px;
    transition: opacity 0.5s ease-in-out;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
}

#popup h2 {
    margin-top: 0;
}

#popup button {
    margin-top: 20px;
    background-color: gray;
    border: none;
}