body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f7f6;
    color: #333;
    line-height: 1.6;
}

header {
    background-color: #2c3e50; /* 深蓝色 */
    color: #ecf0f1; /* 浅色文本 */
    padding: 40px 20px;
    text-align: center;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
}

header h1 {
    margin-top: 0;
    font-size: 2.8em;
    letter-spacing: 1px;
}

header p {
    font-size: 1.1em;
    opacity: 0.8;
}

main {
    max-width: 1200px;
    margin: 30px auto;
    padding: 0 20px;
}

.controls {
    display: flex;
    flex-wrap: wrap; /* 允许换行 */
    gap: 15px; /* 元素之间的间距 */
    margin-bottom: 30px;
    align-items: center;
}

#search-input {
    flex-grow: 1; /* 尽量占据可用空间 */
    padding: 12px 15px;
    border: 1px solid #ccc;
    border-radius: 8px;
    font-size: 1em;
    min-width: 250px; /* 最小宽度 */
    box-sizing: border-box; /* 包含padding和border在宽度内 */
}

#category-filters {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.category-button {
    padding: 10px 20px;
    border: 1px solid #3498db; /* 蓝色边框 */
    border-radius: 20px; /* 圆角胶囊状按钮 */
    background-color: #fff;
    color: #3498db;
    cursor: pointer;
    font-size: 0.9em;
    transition: all 0.3s ease;
    white-space: nowrap; /* 防止按钮文字换行 */
}

.category-button:hover {
    background-color: #e0f2f7; /* 浅蓝色背景 */
    color: #2980b9;
}

.category-button.active {
    background-color: #3498db; /* 选中状态的深蓝色背景 */
    color: #fff;
    border-color: #3498db;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
}

.resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); /* 响应式网格布局 */
    gap: 25px; /* 卡片之间的间距 */
}

.resource-card {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
    padding: 25px;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    display: flex;
    flex-direction: column;
}

.resource-card:hover {
    transform: translateY(-5px); /* 鼠标悬停时上浮 */
    box-shadow: 0 8px 15px rgba(0, 0, 0, 0.15);
}

.resource-card h3 {
    margin-top: 0;
    margin-bottom: 10px;
    color: #2c3e50;
    font-size: 1.4em;
}

.resource-card p {
    font-size: 0.95em;
    color: #666;
    flex-grow: 1; /* 描述占据剩余空间，使按钮对齐底部 */
    margin-bottom: 15px;
}

.resource-card .card-footer {
    margin-top: auto; /* 将footer推到底部 */
    text-align: right;
}

.resource-card .card-footer a {
    display: inline-block;
    padding: 10px 20px;
    background-color: #2ecc71; /* 绿色按钮 */
    color: white;
    text-decoration: none;
    border-radius: 5px;
    font-weight: bold;
    transition: background-color 0.3s ease;
}

.resource-card .card-footer a:hover {
    background-color: #27ae60; /* 鼠标悬停时变深 */
}

#no-results {
    grid-column: 1 / -1; /* 占据所有列 */
    text-align: center;
    font-size: 1.2em;
    color: #777;
    padding: 50px 0;
}

.hidden {
    display: none !important;
}

footer {
    text-align: center;
    padding: 20px;
    margin-top: 50px;
    background-color: #ecf0f1;
    color: #777;
    font-size: 0.9em;
}

/* 响应式调整 */
@media (max-width: 768px) {
    header h1 {
        font-size: 2em;
    }
    header p {
        font-size: 1em;
    }
    .controls {
        flex-direction: column; /* 小屏幕下搜索框和分类按钮垂直排列 */
        align-items: stretch;
    }
    #search-input {
        min-width: unset; /* 取消最小宽度限制 */
        width: 100%;
    }
    #category-filters {
        justify-content: center; /* 分类按钮居中 */
        width: 100%;
    }
    .resources-grid {
        grid-template-columns: 1fr; /* 小屏幕下每行一个卡片 */
    }
}