body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f4f4;
    display: flex;
    min-height: 100vh;
}

.container {
    display: flex;
    width: 100%;
}

.sidebar {
    width: 20%;
    background-color: #333;
    color: white;
    padding: 20px;
    box-sizing: border-box;
}

.sidebar h2 {
    margin-top: 0;
    font-size: 1.5em;
}

.sidebar ul {
    list-style: none;
    padding: 0;
}

.sidebar ul li a {
    color: white;
    text-decoration: none;
    padding: 10px 0;
    display: block;
    transition: background-color 0.3s ease;
}

.sidebar ul li a:hover,
.sidebar ul li a.active {
    background-color: #555;
}

.content {
    width: 80%;
    padding: 20px;
    box-sizing: border-box;
    background-color: white;
    overflow-y: auto;
}

.section {
    display: none;
}

.section.active {
    display: block;
}

.grid-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: 15px;
    margin-top: 20px;
}

.item-card {
    border: 1px solid #ddd;
    padding: 10px;
    text-align: center;
    background-color: #fff;
    border-radius: 5px;
    position: relative;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.item-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 4px 8px rgba(0,0,0,0.15);
}

.item-card svg {
    width: 50px;
    height: 50px;
    margin-bottom: 5px;
}

.item-card .symbol-char {
    font-size: 2em;
    margin-bottom: 5px;
    display: block;
}

.copy-btn {
    position: absolute;
    top: 5px;
    right: 5px;
    background-color: #007bff;
    color: white;
    border: none;
    padding: 3px 6px;
    border-radius: 3px;
    cursor: pointer;
    font-size: 0.8em;
    opacity: 0; /* 默认隐藏 */
    transition: opacity 0.2s ease;
}

.item-card:hover .copy-btn {
    opacity: 1; /* 悬停时显示 */
}

.popup {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    background-color: rgba(0, 0, 0, 0.7);
    color: white;
    padding: 10px 20px;
    border-radius: 5px;
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
}

.popup.show {
    opacity: 1;
    visibility: visible;
}

/* 特殊符号分类标题 */
.category-title {
    grid-column: 1 / -1; /* 让标题占据整行 */
    font-size: 1.3em;
    font-weight: bold;
    margin-top: 20px;
    margin-bottom: 10px;
    text-align: left;
    border-bottom: 1px solid #eee;
    padding-bottom: 5px;
}