body {
    font-family: Arial, sans-serif;
}

form {
    margin: 20px;
}

.popup {
    display: none;
    position: fixed;
    z-index: 1;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0, 0, 0, 0.5);
}

.popup-content {
    background-color: #fff;
    margin: 15% auto;
    padding: 20px;
    border: 1px solid #888;
    width: 80%;
    max-width: 300px;
    text-align: center;
}

.close-btn {
    color: #aaa;
    float: right;
    font-size: 28px;
    font-weight: bold;
}

.close-btn:hover,
.close-btn:focus {
    color: #000;
    text-decoration: none;
    cursor: pointer;
}