body {
    background-image:url('bg.png');
    background-attachment:fixed;
}
.header {
    background-color: orange;
    color: white;
    overflow: hidden;
}
/* 文章卡片效果 */
.card {
    background-color: #ffffff;
    padding: 20px;
    margin-top: 20px;
}

button {
    background-color: orange;
    border: 2px solid orange;
    color: white;
    padding: 16px 32px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
    margin: 4px 2px;
    -webkit-transition-duration: 0.4s;
    transition-duration: 0.4s;
    cursor: pointer;
}

button:hover {
    background-color: white; 
    color: orange; 
    border: 2px solid orange;