/* ===== CSS Variables ===== */
:root {
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-primary-light: #dbeafe;
  --color-text: #1e293b;
  --color-text-muted: #64748b;
  --color-bg: #ffffff;
  --color-bg-alt: #f8fafc;
  --color-border: #e2e8f0;
  --color-footer-bg: #0f172a;
  --color-footer-text: #94a3b8;
  --font-sans: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.1);
  --radius: 12px;
  --max-width: 1100px;
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  font-size: 16px;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: var(--color-primary-dark);
}

img {
  max-width: 100%;
  display: block;
}

/* ===== Header & Nav ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--color-border);
}

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

.logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: 0.02em;
}

.logo:hover {
  color: var(--color-primary);
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 32px;
}

.nav-links a {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  font-weight: 500;
  padding: 4px 0;
  border-bottom: 2px solid transparent;
  transition: color 0.2s, border-color 0.2s;
}

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

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform 0.3s, opacity 0.3s;
}

/* ===== Hero ===== */
.hero {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 80px 24px 64px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: center;
}

.hero-tag {
  display: inline-block;
  background: var(--color-primary-light);
  color: var(--color-primary);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 4px 12px;
  border-radius: 20px;
  margin-bottom: 16px;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 2.75rem);
  font-weight: 800;
  line-height: 1.25;
  margin-bottom: 20px;
  color: var(--color-text);
}

.hero-desc {
  color: var(--color-text-muted);
  font-size: 1.05rem;
  margin-bottom: 32px;
  max-width: 480px;
}

.btn-primary {
  display: inline-block;
  background: var(--color-primary);
  color: #fff;
  padding: 12px 28px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  transition: background 0.2s, transform 0.15s;
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  color: #fff;
  transform: translateY(-1px);
}

.btn-secondary {
  display: inline-block;
  border: 2px solid var(--color-primary);
  color: var(--color-primary);
  padding: 10px 24px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  transition: background 0.2s, color 0.2s;
}

.btn-secondary:hover {
  background: var(--color-primary);
  color: #fff;
}

.hero-visual {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.hero-card {
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 20px 24px;
  display: flex;
  align-items: center;
  gap: 16px;
  transition: box-shadow 0.2s, transform 0.2s;
}

.hero-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateX(4px);
}

.card-icon {
  font-size: 2rem;
  flex-shrink: 0;
}

.hero-card h3 {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 2px;
}

.hero-card p {
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

/* ===== Sections ===== */
.section {
  padding: 64px 0;
}

.section-alt {
  background: var(--color-bg-alt);
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.section-title {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 36px;
  text-align: center;
}

/* ===== Article Grid ===== */
.article-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 24px;
}

.article-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 28px;
  transition: box-shadow 0.2s, transform 0.2s;
}

.section-alt .article-card {
  background: var(--color-bg);
}

.article-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
}

.tag {
  background: var(--color-primary-light);
  color: var(--color-primary);
  font-size: 0.75rem;
  font-weight: 600;
  padding: 2px 10px;
  border-radius: 20px;
}

.article-meta time {
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

.article-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 10px;
  line-height: 1.4;
}

.article-card h3 a {
  color: var(--color-text);
}

.article-card h3 a:hover {
  color: var(--color-primary);
}

.article-card p {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  margin-bottom: 16px;
}

.read-more {
  font-size: 0.875rem;
  font-weight: 600;
}

/* ===== About Brief ===== */
.about-brief {
  max-width: 640px;
  margin: 0 auto;
  text-align: center;
}

.about-brief p {
  color: var(--color-text-muted);
  font-size: 1.05rem;
  margin-bottom: 24px;
}

/* ===== Page Header ===== */
.page-header {
  background: linear-gradient(135deg, var(--color-primary-light) 0%, #eff6ff 100%);
  padding: 56px 24px 48px;
  text-align: center;
}

.page-header h1 {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 12px;
}

.page-header p {
  color: var(--color-text-muted);
  font-size: 1.05rem;
  max-width: 560px;
  margin: 0 auto;
}

/* ===== Article Content ===== */
.article-content {
  max-width: 720px;
  margin: 0 auto;
  padding: 48px 24px 64px;
}

.article-content h2 {
  font-size: 1.35rem;
  font-weight: 700;
  margin: 36px 0 12px;
  color: var(--color-text);
}

.article-content h3 {
  font-size: 1.1rem;
  font-weight: 600;
  margin: 24px 0 8px;
}

.article-content p {
  margin-bottom: 16px;
  color: var(--color-text);
}

.article-content ul,
.article-content ol {
  margin: 0 0 16px 24px;
  color: var(--color-text);
}

.article-content li {
  margin-bottom: 8px;
}

.article-content blockquote {
  border-left: 4px solid var(--color-primary);
  padding: 12px 20px;
  background: var(--color-bg-alt);
  border-radius: 0 8px 8px 0;
  margin: 24px 0;
  color: var(--color-text-muted);
  font-style: italic;
}

.article-header-meta {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--color-border);
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 24px;
  color: var(--color-text-muted);
}

.back-link:hover {
  color: var(--color-primary);
}

/* ===== About Page ===== */
.about-content {
  max-width: 720px;
  margin: 0 auto;
  padding: 48px 24px 64px;
}

.about-content h2 {
  font-size: 1.35rem;
  font-weight: 700;
  margin: 32px 0 12px;
}

.about-content p {
  margin-bottom: 16px;
  color: var(--color-text-muted);
}

.about-box {
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px;
  margin: 24px 0;
}

.about-box p {
  margin-bottom: 0;
  font-size: 0.95rem;
}

/* ===== Footer ===== */
.site-footer {
  background: var(--color-footer-bg);
  color: var(--color-footer-text);
  padding: 48px 24px 32px;
}

.footer-container {
  max-width: var(--max-width);
  margin: 0 auto;
  text-align: center;
}

.footer-site-name {
  font-size: 1.1rem;
  font-weight: 700;
  color: #e2e8f0;
  margin-bottom: 4px;
}

.footer-desc {
  font-size: 0.875rem;
  margin-bottom: 24px;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin-bottom: 20px;
}

.footer-links a {
  color: var(--color-footer-text);
  font-size: 0.875rem;
}

.footer-links a:hover {
  color: #e2e8f0;
}

.footer-beian {
  margin-bottom: 12px;
}

.footer-beian a {
  color: var(--color-footer-text);
  font-size: 0.875rem;
}

.footer-beian a:hover {
  color: #e2e8f0;
}

.footer-copy {
  font-size: 0.8rem;
  color: #64748b;
}

/* ===== Mobile Nav ===== */
@media (max-width: 768px) {
  .nav-toggle {
    display: flex;
  }

  .nav-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--color-bg);
    flex-direction: column;
    gap: 0;
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-md);
  }

  .nav-links.open {
    display: flex;
  }

  .nav-links li a {
    display: block;
    padding: 16px 24px;
    border-bottom: 1px solid var(--color-border);
  }

  .hero {
    grid-template-columns: 1fr;
    padding: 48px 24px 40px;
    gap: 32px;
  }

  .hero-visual {
    flex-direction: row;
    flex-wrap: wrap;
  }

  .hero-card {
    flex: 1 1 calc(50% - 8px);
    min-width: 140px;
    flex-direction: column;
    text-align: center;
    padding: 16px;
  }

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