body {
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    background-attachment: fixed;
}

.sidebar {
    position: fixed;
    left: 0;
    top: 0;
    width: 250px;
    height: 100%;
    background-color: rgba(255, 255, 255, 0.1); /* 半透明白色背景 */
    backdrop-filter: blur(10px); /* 毛玻璃效果 */
    padding: 20px;
    color: #333;
    box-shadow: 2px 0 5px rgba(0,0,0,0.2);
    display: flex;
    flex-direction: column;
    align-items: flex-start;
}

.sidebar h1 {
    color: #333; /* 改为深色 */
    margin-bottom: 30px;
}

.nav-btn {
    display: block;
    width: 80%;
    padding: 10px 15px;
    margin-bottom: 10px;
    text-decoration: none;
    color: black;
    background-color: rgba(255, 255, 255, 0.7); /* 白色略透明 */
    border-radius: 5px;
    transition: background-color 0.3s ease;
    text-align: left;
}

.nav-btn:hover {
    background-color: rgba(255, 255, 255, 0.9); /* 鼠标悬停时透明度降低 */
}

#playlist-select {
    background-color: rgba(255, 255, 255, 0.7); /* 白色略透明 */
    border: none;
    border-radius: 10px; /* 圆角 */
    padding: 8px 12px;
    margin-bottom: 15px;
    font-size: 16px;
    color: #333;
    outline: none;
    cursor: pointer;
}

#playlist-select:hover {
    background-color: rgba(255, 255, 255, 0.9); /* 鼠标悬停时透明度降低 */
}

.main-content {
    margin-left: 270px; /* 留出侧边栏的空间 */
    padding: 20px;
    color: #333; /* 改为深色 */
}

#back-to-top {
    display: none; /* Hidden by default */
    position: fixed; /* Fixed/sticky position */
    bottom: 20px; /* Place the button at the bottom of the page */
    right: 20px; /* Place the button 20px from the right */
    z-index: 99; /* Make sure it does not overlap */
    font-size: 18px; /* Increase font size */
    border: none; /* Remove borders */
    outline: none; /* Remove outline */
    background-color: rgba(255, 255, 255, 0.7); /* Set a background color */
    color: #333; /* Text color */
    cursor: pointer; /* Add a mouse pointer on hover */
    padding: 15px; /* Some padding */
    border-radius: 50%; /* Rounded corners */
    transition: background-color 0.3s ease; /* Smooth transition for hover effect */
}

#back-to-top:hover {
    background-color: rgba(255, 255, 255, 0.9); /* Darker background on hover */
}