/* 全局样式 */
body {
    font-family: 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    margin: 0;
    padding: 0;
    background-color: #f5f7fa;
    color: #333;
}

header {
    background-color: #0a2e5a;
    color: white;
    padding: 2rem;
    text-align: center;
}

.logo {
    height: 200px;
    margin-bottom: 1rem;
}

.button-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    padding: 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

.category-card {
    display: block;
    padding: 2rem;
    border-radius: 8px;
    text-align: center;
    color: white;
    text-decoration: none;
    transition: transform 0.3s;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
}

.category-card:hover {
    transform: translateY(-5px);
}

.category-card h2 {
    font-size: 1.8rem;
    margin-bottom: 0.5rem;
}

.category-card p {
    opacity: 0.9;
}

/* 各类别颜色 */
.math { background: linear-gradient(135deg, #4b6cb7, #182848); }
.toolbox { background: linear-gradient(135deg, #11998e, #38ef7d); }
.entertainment { background: linear-gradient(135deg, #f46b45, #eea849); }

footer {
    text-align: center;
    padding: 1.5rem;
    background: #333;
    color: #fff;
    margin-top: 2rem;
}