body.dark-mode {
    background: #2d3436;
    color: #e0e0e0;
}
body.dark-mode .status-box {
    background: linear-gradient(145deg, #2d3436, #3a3a3a);
    border: 1px solid #444;
}
body.dark-mode .time-display {
    color: #ecf0f1;
}
body.dark-mode .status-label {
    color: #bdc3c7;
}
body.dark-mode .schedule-table {
    background: #3a3a3a;
}
body.dark-mode .schedule-table th {
    background: #444;
    color: #ecf0f1;
}
body.dark-mode .schedule-table td {
    border-bottom: 1px solid #555;
}
body.dark-mode .current-class {
    background: #34495e !important;
}
body.dark-mode .future-class {
    background: #3a3a3a !important;
}
body.dark-mode .past-class {
    background: #2d3436 !important;
    color: #7f8c8d;
}
body.dark-mode .control-btn {
    background: linear-gradient(135deg, #2980b9, #3498db);
}
body.dark-mode .control-btn:hover {
    box-shadow: 0 6px 16px rgba(52, 152, 219, 0.35);
}
body.dark-mode .settings-panel {
    background: rgba(45, 52, 54, 0.95);
    border: 1px solid #444;
}
body.dark-mode .settings-panel h3 {
    color: #ecf0f1;
}
body.dark-mode .settings-panel label {
    color: #bdc3c7;
}
body.dark-mode .settings-panel input[type="number"] {
    background: #3a3a3a;
    color: #ecf0f1;
    border: 1px solid #555;
}
body.dark-mode .settings-panel input[type="file"] {
    background: #3a3a3a;
    color: #ecf0f1;
    border: 1px solid #555;
}
body.dark-mode .file-input-label {
    background: #27ae60;
}
body.dark-mode .file-input-label:hover {
    background: #219150;
}
body.dark-mode .info-container {
    background: #2980b9;
}
body.dark-mode .info-content:before {
    color: #2980b9;
}
body.dark-mode .error-container {
    background: #c0392b;
}
body.dark-mode .error-content:before {
    color: #c0392b;
}
body.dark-mode .reminder-table {
    background: #3a3a3a;
}
body.dark-mode .reminder-table th {
    background: #444;
    color: #ecf0f1;
}
body.dark-mode .reminder-table td {
    border-bottom: 1px solid #555;
}
body.dark-mode .reminder-table td input,
body.dark-mode .reminder-table td select {
    background: #3a3a3a;
    color: #ecf0f1;
    border: 1px solid #555;
}
body.dark-mode .reminder-table td button {
    background: #e74c3c;
}
body.dark-mode .reminder-table td button:hover {
    background: #c0392b;
}
body.dark-mode .action-btn {
    background: #27ae60;
}
body.dark-mode .action-btn:hover {
    box-shadow: 0 6px 16px rgba(39, 174, 96, 0.35);
}

#return-btn {
    position: absolute; /* 绝对定位 */
    top: 20px; /* 距离顶部 20px */
    left: 20px; /* 距离左侧 20px */
    background-color: #f5f7fa; /* 默认亮色模式背景颜色 */
    color: #333333; /* 默认亮色模式文字颜色 */
    border: 1px solid #cccccc; /* 默认亮色模式边框颜色 */
    border-radius: 16px; /* 按钮圆角大小 */
    padding: 10px 18px; /* 按钮内边距 */
    font-size: 14px; /* 按钮字体大小 */
    cursor: pointer; /* 鼠标悬停时显示为手型 */
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.2); /* 按钮阴影 */
    transition: background-color 0.3s ease, transform 0.3s ease; /* 背景颜色和缩放的过渡效果 */
    z-index: 1001; /* 按钮层级 */
}

#return-btn:hover {
    background-color: #e0e4e8; /* 默认亮色模式悬停背景颜色 */
    transform: scale(1.05); /* 悬停时放大 5% */
}

/* 暗色模式 */
body.dark-mode #return-btn {
    background-color: #4a4f55; /* 更浅的暗色模式背景颜色 */
    color: #e0e0e0; /* 暗色模式文字颜色 */
    border: 1px solid #555555; /* 更浅的暗色模式边框颜色 */
}

body.dark-mode #return-btn:hover {
    background-color: #3b4046; /* 更浅的暗色模式悬停背景颜色 */
}