/* ==================== 全局样式 ==================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* 主题色 */
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --accent-color: #0ea5e9;

    /* 背景色 */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;

    /* 文字色 */
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;

    /* 边框色 */
    --border-color: #e2e8f0;
    --border-hover: #cbd5e1;

    /* 阴影 */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);

    /* 其他 */
    --radius: 8px;
    --radius-lg: 12px;
    --transition: all 0.3s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-secondary);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ==================== 顶部导航 ==================== */
.header {
    background: linear-gradient(135deg, #2563eb 0%, #0ea5e9 100%);
    color: white;
    padding: 2rem 0;
    box-shadow: var(--shadow-md);
}

.header-content {
    text-align: center;
}

.logo {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.logo-icon {
    font-size: 2.5rem;
}

.subtitle {
    font-size: 0.95rem;
    opacity: 0.9;
    font-weight: 300;
    letter-spacing: 0.5px;
}

.back-link {
    display: inline-block;
    color: white;
    text-decoration: none;
    margin-bottom: 1rem;
    opacity: 0.9;
    transition: var(--transition);
}

.back-link:hover {
    opacity: 1;
    transform: translateX(-4px);
}

/* ==================== 主内容区 ==================== */
.main {
    flex: 1;
    padding: 2rem 0;
}

/* ==================== 工具栏 ==================== */
.toolbar {
    background: var(--bg-primary);
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    margin-bottom: 2rem;
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    align-items: center;
}

.search-box {
    flex: 1;
    min-width: 300px;
    display: flex;
    gap: 0.5rem;
}

.search-input {
    flex: 1;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 0.95rem;
    transition: var(--transition);
}

.search-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.search-btn {
    padding: 0.75rem 1.5rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius);
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.search-btn:hover {
    background: var(--primary-hover);
}

.filter-box {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.category-select {
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 0.95rem;
    background: white;
    cursor: pointer;
    transition: var(--transition);
}

.category-select:focus {
    outline: none;
    border-color: var(--primary-color);
}

/* ==================== 论文列表（宽布局） ==================== */
.papers-grid {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.paper-card {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: 2rem;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    cursor: pointer;
    border: 2px solid transparent;
    display: flex;
    gap: 2rem;
    align-items: flex-start;
}

.paper-card:hover {
    transform: translateX(8px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.paper-card-content {
    flex: 1;
    min-width: 0;
}

.paper-card-header {
    margin-bottom: 1rem;
}

.paper-card-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
    line-height: 1.4;
}

.paper-card-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
}

.meta-item {
    display: flex;
    align-items: center;
    gap: 0.35rem;
}

.meta-item i {
    color: var(--primary-color);
}

.category-badge {
    display: inline-block;
    padding: 0.4rem 1rem;
    background: var(--bg-tertiary);
    color: var(--primary-color);
    border-radius: 999px;
    font-size: 0.85rem;
    font-weight: 500;
    line-height: 1.4;
    vertical-align: middle;
    white-space: nowrap;
}

.paper-card-abstract {
    color: var(--text-secondary);
    font-size: 0.9rem;
    line-height: 1.6;
    margin-bottom: 1rem;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.paper-card-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
}

.file-type-badge {
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius);
    font-size: 0.8rem;
    font-weight: 500;
}

.file-type-pdf {
    background: #fee2e2;
    color: #dc2626;
}

.file-type-markdown {
    background: #dbeafe;
    color: #2563eb;
}

.view-paper-btn {
    color: var(--primary-color);
    font-weight: 500;
    text-decoration: none;
    font-size: 0.9rem;
    transition: var(--transition);
}

.view-paper-btn:hover {
    color: var(--primary-hover);
}

/* ==================== 论文详情页 ==================== */
.paper-detail {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: 2rem;
    box-shadow: var(--shadow-md);
}

.paper-meta {
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 2rem;
    margin-bottom: 2rem;
}

.paper-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    line-height: 1.3;
}

.paper-info {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.info-item {
    display: flex;
    gap: 0.5rem;
    align-items: baseline;
}

.info-label {
    font-weight: 600;
    color: var(--text-secondary);
    white-space: nowrap; /* 防止"作者"等标签换行 */
    flex-shrink: 0; /* 标签不被压缩 */
}

.info-value {
    color: var(--text-primary);
    flex: 1; /* 内容可以自动换行 */
}

.paper-abstract {
    background: var(--bg-secondary);
    padding: 1.5rem;
    border-radius: var(--radius);
    margin-bottom: 1.5rem;
}

.paper-abstract h3 {
    margin-bottom: 0.75rem;
    color: var(--text-secondary);
}

.paper-actions {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    display: inline-block;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
}

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: var(--border-color);
}

/* ==================== Markdown 内容样式 ==================== */
.markdown-body {
    font-size: 1rem;
    line-height: 1.8;
    color: var(--text-primary);
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3,
.markdown-body h4 {
    margin-top: 1.5rem;
    margin-bottom: 1rem;
    font-weight: 600;
}

.markdown-body h1 {
    font-size: 2rem;
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 0.5rem;
}

.markdown-body h2 {
    font-size: 1.5rem;
}

.markdown-body h3 {
    font-size: 1.25rem;
}

.markdown-body p {
    margin-bottom: 1rem;
}

.markdown-body code {
    background: var(--bg-tertiary);
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 0.9em;
}

.markdown-body pre {
    background: var(--bg-tertiary);
    padding: 1rem;
    border-radius: var(--radius);
    overflow-x: auto;
    margin-bottom: 1rem;
}

.markdown-body pre code {
    background: none;
    padding: 0;
}

.markdown-body blockquote {
    border-left: 4px solid var(--primary-color);
    padding-left: 1rem;
    margin: 1rem 0;
    color: var(--text-secondary);
}

.markdown-body img {
    max-width: 100%;
    height: auto;
    border-radius: var(--radius);
    display: block;
    margin: 1.5rem auto;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.markdown-body img:hover {
    box-shadow: var(--shadow-lg);
    transform: scale(1.02);
}

/* 图片标题样式（使用 title 属性或 alt 文本） */
.markdown-body img[title]::after,
.markdown-body img[alt]::after {
    content: attr(title);
    display: block;
    text-align: center;
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-top: 0.5rem;
    font-style: italic;
}

.markdown-body table {
    width: 100%;
    border-collapse: collapse;
    margin: 1rem 0;
}

.markdown-body th,
.markdown-body td {
    border: 1px solid var(--border-color);
    padding: 0.75rem;
    text-align: left;
}

.markdown-body th {
    background: var(--bg-tertiary);
    font-weight: 600;
}

/* ==================== PDF 查看器 ==================== */
.pdf-viewer {
    margin-top: 2rem;
}

.pdf-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
    justify-content: center;
    padding: 1rem;
    background: var(--bg-tertiary);
    border-radius: var(--radius);
    margin-bottom: 1rem;
}

.btn-icon {
    padding: 0.5rem 1rem;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
}

.btn-icon:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

#pdfCanvas {
    display: block;
    margin: 0 auto;
    max-width: 100%;
    box-shadow: var(--shadow-lg);
    border-radius: var(--radius);
}

/* ==================== 加载和状态 ==================== */
.loading {
    text-align: center;
    padding: 3rem;
}

.spinner {
    width: 50px;
    height: 50px;
    margin: 0 auto 1rem;
    border: 4px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.error-message {
    text-align: center;
    padding: 3rem;
    color: #dc2626;
}

.empty-state {
    text-align: center;
    padding: 3rem;
    color: var(--text-muted);
    font-size: 1.1rem;
}

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

.footer-note {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-top: 0.5rem;
}

/* ==================== 响应式设计 ==================== */
@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }

    .logo {
        font-size: 1.5rem;
    }

    .back-link {
        font-size: 0.9rem;
    }

    .toolbar {
        flex-direction: column;
    }

    .search-box {
        width: 100%;
    }

    .papers-grid {
        grid-template-columns: 1fr;
    }

    .paper-title {
        font-size: 1.5rem;
    }

    .paper-info {
        grid-template-columns: 1fr;
    }

    .paper-meta {
        padding: 1rem;
    }

    /* PDF控制工具栏移动端优化 ✅ */
    .pdf-controls {
        flex-wrap: wrap; /* 允许换行 */
        gap: 0.5rem;
        padding: 0.75rem;
        justify-content: center;
    }

    .btn-icon {
        padding: 0.5rem 0.75rem;
        font-size: 0.9rem;
        min-width: 44px; /* 触摸友好的最小尺寸 */
        min-height: 44px;
    }

    /* 页码信息和缩放级别在移动端缩小 */
    #pageInfo, #zoomLevel {
        font-size: 0.85rem;
        white-space: nowrap;
    }

    /* PDF画布移动端优化 */
    .pdf-viewer {
        margin-top: 1rem;
    }

    #pdfCanvas {
        max-width: 100%;
        height: auto;
    }

    /* 操作按钮在移动端堆叠 */
    .paper-actions {
        flex-direction: column;
    }

    .paper-actions .btn {
        width: 100%;
    }

    /* Markdown内容移动端优化 */
    .markdown-body {
        font-size: 0.95rem;
        padding: 1rem;
    }

    .markdown-body img {
        max-width: 100%;
        height: auto;
    }

    .markdown-body table {
        display: block;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
    }
}