/* ========== CSS 变量（亮色/暗色主题） ========== */
:root {
    --bg: #ffffff;
    --bg-secondary: #f8f9fa;
    --text: #1a1a2e;
    --text-secondary: #555;
    --accent: #4f46e5;
    --accent-light: #eef2ff;
    --border: #e5e7eb;
    --card-shadow: 0 4px 20px rgba(0,0,0,0.06);
    --card-hover-shadow: 0 8px 40px rgba(0,0,0,0.12);
    --radius: 16px;
}

[data-theme="dark"] {
    --bg: #0f0f23;
    --bg-secondary: #1a1a3e;
    --text: #e2e8f0;
    --text-secondary: #a0aec0;
    --accent: #818cf8;
    --accent-light: #1e1b4b;
    --border: #2d3748;
    --card-shadow: 0 4px 20px rgba(0,0,0,0.3);
    --card-hover-shadow: 0 8px 40px rgba(0,0,0,0.5);
}

/* ========== 基础重置 ========== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Microsoft YaHei', sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.7;
    transition: background 0.3s, color 0.3s;
}

a {
    color: var(--accent);
    text-decoration: none;
    transition: opacity 0.2s;
}
a:hover { opacity: 0.8; }

/* ========== 导航栏 ========== */
.navbar {
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    backdrop-filter: blur(12px);
    background: rgba(255,255,255,0.85);
}

[data-theme="dark"] .navbar {
    background: rgba(15,15,35,0.85);
}

.nav-container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 24px;
    height: 64px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--text);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 24px;
}

.nav-links a {
    color: var(--text-secondary);
    font-size: 0.95rem;
    padding: 4px 0;
    border-bottom: 2px solid transparent;
    transition: all 0.2s;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--accent);
    border-bottom-color: var(--accent);
}

.theme-btn {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 50%;
    width: 38px;
    height: 38px;
    font-size: 1.1rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.3s, background 0.3s;
}
.theme-btn:hover { transform: rotate(20deg) scale(1.1); }

/* ========== Hero 横幅 ========== */
.hero {
    background: linear-gradient(135deg, var(--accent) 0%, #7c3aed 100%);
    padding: 80px 24px;
    text-align: center;
}

.hero-content h1 {
    font-size: 2.5rem;
    color: white;
    margin-bottom: 12px;
}

.hero-content p {
    font-size: 1.15rem;
    color: rgba(255,255,255,0.85);
    margin-bottom: 20px;
}

.hero-tags {
    display: flex;
    gap: 10px;
    justify-content: center;
    flex-wrap: wrap;
}

.tag {
    background: rgba(255,255,255,0.2);
    color: white;
    padding: 6px 16px;
    border-radius: 20px;
    font-size: 0.85rem;
}

/* ========== 主容器 ========== */
.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 40px 24px;
}

/* ========== 筛选标签 ========== */
.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 32px;
    flex-wrap: wrap;
    gap: 16px;
}

.section-header h2 {
    font-size: 1.5rem;
}

.filter-tags {
    display: flex;
    gap: 8px;
}

.filter-btn {
    padding: 6px 16px;
    border-radius: 20px;
    border: 1px solid var(--border);
    background: var(--bg);
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 0.85rem;
    transition: all 0.2s;
}

.filter-btn:hover,
.filter-btn.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

/* ========== 文章卡片网格 ========== */
.post-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 24px;
}

.post-card {
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 28px;
    transition: all 0.3s ease;
    cursor: pointer;
    box-shadow: var(--card-shadow);
}

.post-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--card-hover-shadow);
    border-color: var(--accent);
}

.post-card .post-meta {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 12px;
    font-size: 0.82rem;
    color: var(--text-secondary);
}

.post-card .post-tag {
    background: var(--accent-light);
    color: var(--accent);
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 500;
}

.post-card h3 {
    font-size: 1.15rem;
    margin-bottom: 10px;
    line-height: 1.4;
}

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

.post-card .read-more {
    display: inline-block;
    margin-top: 16px;
    color: var(--accent);
    font-size: 0.85rem;
    font-weight: 500;
}

/* ========== 文章详情页 ========== */
.post-page {
    padding-top: 24px;
}

.back-link {
    display: inline-block;
    margin-bottom: 24px;
    color: var(--text-secondary);
    font-size: 0.9rem;
}
.back-link:hover { color: var(--accent); }

.post-content {
    max-width: 720px;
    margin: 0 auto;
}

.post-content h1 {
    font-size: 2rem;
    margin-bottom: 16px;
    line-height: 1.3;
}

.post-content .post-info {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 32px;
    padding-bottom: 24px;
    border-bottom: 1px solid var(--border);
}

.post-content .post-body h2 {
    font-size: 1.4rem;
    margin: 32px 0 16px;
    color: var(--accent);
}

.post-content .post-body p {
    margin-bottom: 16px;
    line-height: 1.9;
}

.post-content .post-body code {
    background: var(--bg-secondary);
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 0.9em;
    font-family: 'Fira Code', monospace;
}

.post-content .post-body pre {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: 12px;
    overflow-x: auto;
    margin: 20px 0;
    border: 1px solid var(--border);
}

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

/* ========== 关于页 ========== */
.about-page {
    display: flex;
    justify-content: center;
    padding-top: 60px;
}

.about-card {
    text-align: center;
    max-width: 600px;
}

.about-avatar {
    font-size: 5rem;
    margin-bottom: 20px;
}

.about-card h1 {
    font-size: 2rem;
    margin-bottom: 16px;
}

.about-desc {
    color: var(--text-secondary);
    font-size: 1.05rem;
    line-height: 1.8;
    margin-bottom: 32px;
}

.about-info {
    text-align: left;
    background: var(--bg-secondary);
    border-radius: var(--radius);
    padding: 32px;
}

.about-info h3 {
    margin-bottom: 12px;
    margin-top: 20px;
}
.about-info h3:first-child { margin-top: 0; }

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.skill {
    background: var(--accent-light);
    color: var(--accent);
    padding: 6px 14px;
    border-radius: 8px;
    font-size: 0.85rem;
}

/* ========== 页脚 ========== */
.footer {
    text-align: center;
    padding: 40px 24px;
    border-top: 1px solid var(--border);
    margin-top: 60px;
}

.footer-content p {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.footer-sub {
    font-size: 0.8rem !important;
    margin-top: 4px;
    opacity: 0.6;
}

/* ========== 响应式 ========== */
@media (max-width: 768px) {
    .hero-content h1 { font-size: 1.8rem; }
    .post-grid { grid-template-columns: 1fr; }
    .section-header { flex-direction: column; align-items: flex-start; }
    .nav-links { gap: 16px; }
}

/* ========== 动画 ========== */
@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.post-card {
    animation: fadeInUp 0.5s ease forwards;
}

.post-card:nth-child(2) { animation-delay: 0.1s; }
.post-card:nth-child(3) { animation-delay: 0.2s; }
.post-card:nth-child(4) { animation-delay: 0.3s; }