/* --- 视觉升级：典雅的学者书房 --- */

/* --- 全局样式与字体 --- */
:root {
    --bg-color: #111827; /* 午夜蓝 */
    --card-bg: #1F2937; /* 石板灰 */
    --accent-gold: #D4AF37; /* 复古金 */
    --text-primary: #F9FAFB; /* 米白 */
    --text-secondary: #9CA3AF; /* 淡灰 */
    --border-color: #374151;
}

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: 'Noto Serif SC', serif;
    line-height: 1.8;
    margin: 0;
    padding: 0;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3 {
    font-family: 'Playfair Display', serif;
    font-weight: 700;
    color: var(--text-primary);
    text-rendering: optimizeLegibility;
}

/* --- 页头 --- */
header {
    text-align: center;
    padding: 5rem 2rem;
    background: linear-gradient(135deg, rgba(17, 24, 39, 0.8), rgba(31, 41, 55, 0.5)), url('https://www.transparenttextures.com/patterns/dark-denim-3.png');
    border-bottom: 1px solid var(--border-color);
}

header h1 {
    font-size: 4rem;
    margin-bottom: 1rem;
    letter-spacing: 3px;
    text-shadow: 0 2px 10px rgba(0,0,0,0.5);
}

header p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
    font-style: italic;
}

/* --- 书籍网格布局 --- */
.book-grid {
    max-width: 1400px;
    margin: 4rem auto;
    padding: 0 2rem;
}

.category {
    margin-bottom: 5rem;
}

.category h2 {
    font-size: 2.8rem;
    margin-bottom: 3rem;
    text-align: center;
    position: relative;
    padding-bottom: 1.5rem;
}

/* 分类标题装饰线 */
.category h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 2px;
    background: var(--accent-gold);
    box-shadow: 0 0 15px var(--accent-gold);
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 3rem;
}

/* --- 书籍卡片 --- */
.book-card {
    background-color: var(--card-bg);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.4);
    border: 1px solid var(--border-color);
    transition: transform 0.4s cubic-bezier(0.25, 0.8, 0.25, 1), 
                box-shadow 0.4s cubic-bezier(0.25, 0.8, 0.25, 1), 
                border-color 0.4s ease;
    display: flex;
    flex-direction: column;
    opacity: 0;
    transform: translateY(30px);
    animation: fadeIn 0.6s forwards;
}

.book-card:hover {
    transform: translateY(-12px) scale(1.02);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.6);
    border-color: var(--accent-gold);
}

/* --- 模拟书籍封面 (升级版) --- */
.book-cover {
    background: linear-gradient(145deg, #3a3a3a, #2a2a2a);
    padding: 2.5rem 2rem;
    text-align: center;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 240px;
    position: relative;
    border-bottom: 1px solid var(--border-color);
    box-shadow: inset 0 -10px 20px -10px rgba(0,0,0,0.5);
}

/* 模拟书脊 */
.book-cover::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    width: 15px;
    background: linear-gradient(to right, rgba(0,0,0,0.4), rgba(0,0,0,0));
}

.cover-title {
    font-family: 'Noto Serif SC', serif;
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
    text-shadow: 0 1px 5px rgba(0,0,0,0.3);
}

.cover-author {
    font-size: 1.1rem;
    color: var(--text-secondary);
}

/* --- 书籍信息 --- */
.book-info {
    padding: 2rem;
    flex-grow: 1;
    display: flex;
    flex-direction: column;
}

.book-info h3 {
    font-size: 1.6rem;
    margin-top: 0;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.book-info .author {
    color: var(--accent-gold);
    font-weight: bold;
    margin-bottom: 1.5rem;
    font-size: 1.05rem;
}

.book-info .reason {
    font-size: 1rem;
    color: var(--text-secondary);
    flex-grow: 1;
}

/* --- 页脚 --- */
footer {
    text-align: center;
    padding: 3rem 2rem;
    margin-top: 4rem;
    background-color: #0c1220;
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
}

/* --- 动画 --- */
@keyframes fadeIn {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* --- 响应式设计 --- */
@media (max-width: 768px) {
    header h1 {
        font-size: 3rem;
    }
    .category h2 {
        font-size: 2.2rem;
    }
    .category-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }
}