/* ========== DV4 - 全局样式 ========== */
:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-light: #dbeafe;
  --bg: #f8fafc;
  --card-bg: #ffffff;
  --text: #1e293b;
  --text-light: #64748b;
  --border: #e2e8f0;
  --shadow: 0 1px 3px rgba(0,0,0,0.08);
  --radius: 8px;
  --max-width: 960px;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.75;
  font-size: 16px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ========== 导航栏 ========== */
.navbar {
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 2px rgba(0,0,0,0.04);
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
}

.nav-brand {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
  letter-spacing: 0.5px;
}

.nav-brand:hover {
  color: var(--primary-dark);
}

.nav-links {
  display: flex;
  gap: 8px;
  list-style: none;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-light);
  padding: 6px 14px;
  border-radius: 6px;
  font-size: 0.9rem;
  font-weight: 500;
  transition: all 0.2s;
}

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

/* 移动端汉堡菜单 */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text);
  margin: 5px 0;
  transition: 0.3s;
}

@media (max-width: 768px) {
  .nav-toggle {
    display: block;
  }
  .nav-links {
    display: none;
    position: absolute;
    top: 56px;
    left: 0;
    right: 0;
    background: var(--card-bg);
    flex-direction: column;
    padding: 12px 20px;
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow);
  }
  .nav-links.open {
    display: flex;
  }
}

/* ========== 主内容区 ========== */
main {
  flex: 1;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 32px 20px 60px;
  width: 100%;
}

/* ========== 首页 Hero ========== */
.hero {
  text-align: center;
  padding: 48px 0 32px;
}

.hero h1 {
  font-size: 2rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 12px;
}

.hero h1 span {
  color: var(--primary);
}

.hero p {
  color: var(--text-light);
  font-size: 1.05rem;
  max-width: 560px;
  margin: 0 auto;
  line-height: 1.8;
}

/* ========== 卡片 ========== */
.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  margin-bottom: 16px;
  transition: box-shadow 0.2s, transform 0.2s;
}

.card:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

.card h3 {
  font-size: 1.1rem;
  margin-bottom: 6px;
}

.card h3 a {
  color: var(--text);
  text-decoration: none;
}

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

.card-meta {
  font-size: 0.82rem;
  color: var(--text-light);
  margin-bottom: 8px;
}

.card p {
  color: var(--text-light);
  font-size: 0.93rem;
  line-height: 1.7;
}

/* ========== 文章页 ========== */
.article-header {
  margin-bottom: 32px;
}

.article-header h1 {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.article-header .meta {
  color: var(--text-light);
  font-size: 0.85rem;
}

.article-body h2 {
  font-size: 1.25rem;
  margin: 28px 0 10px;
  color: var(--text);
}

.article-body h3 {
  font-size: 1.1rem;
  margin: 22px 0 8px;
}

.article-body p {
  margin-bottom: 16px;
  line-height: 1.85;
}

.article-body ul,
.article-body ol {
  margin: 0 0 16px 20px;
}

.article-body li {
  margin-bottom: 6px;
}

.article-body pre {
  background: #1e293b;
  color: #e2e8f0;
  padding: 16px;
  border-radius: 6px;
  overflow-x: auto;
  font-size: 0.88rem;
  margin-bottom: 16px;
  line-height: 1.6;
}

.article-body code {
  background: #f1f5f9;
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.88em;
  color: var(--primary-dark);
}

.article-body pre code {
  background: none;
  color: #e2e8f0;
  padding: 0;
}

.article-body blockquote {
  border-left: 3px solid var(--primary);
  padding: 8px 16px;
  margin: 16px 0;
  background: var(--primary-light);
  border-radius: 0 6px 6px 0;
  color: var(--text);
}

.back-link {
  display: inline-block;
  margin-top: 32px;
  color: var(--primary);
  text-decoration: none;
  font-weight: 500;
  font-size: 0.93rem;
}

.back-link:hover {
  text-decoration: underline;
}

/* ========== 页面通用标题 ========== */
.page-title {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.page-subtitle {
  color: var(--text-light);
  margin-bottom: 32px;
  font-size: 1rem;
}

/* ========== 关于我 / 隐私政策 ========== */
.content-section h2 {
  font-size: 1.25rem;
  margin: 28px 0 10px;
  color: var(--text);
}

.content-section p {
  margin-bottom: 14px;
  line-height: 1.85;
}

.content-section ul {
  margin: 0 0 16px 20px;
}

.content-section li {
  margin-bottom: 6px;
}

/* ========== 广告占位 ========== */
.ad-placeholder {
  display: none;
  background: var(--card-bg);
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  padding: 28px 20px;
  text-align: center;
  color: #94a3b8;
  font-size: 0.82rem;
  margin: 24px 0;
  letter-spacing: 0.5px;
}

/* ========== 页脚 ========== */
.footer {
  background: var(--card-bg);
  border-top: 1px solid var(--border);
  padding: 24px 20px;
  text-align: center;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

.footer p {
  color: var(--text-light);
  font-size: 0.82rem;
  line-height: 1.8;
}

.footer a {
  color: var(--primary);
  text-decoration: none;
}

.footer a:hover {
  text-decoration: underline;
}

/* ========== 标签 ========== */
.tag {
  display: inline-block;
  background: var(--primary-light);
  color: var(--primary-dark);
  padding: 2px 10px;
  border-radius: 12px;
  font-size: 0.78rem;
  font-weight: 500;
  margin-right: 6px;
}

/* ========== 按钮 ========== */
.btn {
  display: inline-block;
  padding: 10px 24px;
  background: var(--primary);
  color: #fff;
  border-radius: 6px;
  text-decoration: none;
  font-weight: 500;
  font-size: 0.93rem;
  transition: background 0.2s;
  border: none;
  cursor: pointer;
}

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

.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 1px solid var(--primary);
}

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

/* ========== 响应式 ========== */
@media (max-width: 640px) {
  main {
    padding: 20px 16px 40px;
  }
  .hero {
    padding: 32px 0 20px;
  }
  .hero h1 {
    font-size: 1.5rem;
  }
  .article-header h1,
  .page-title {
    font-size: 1.4rem;
  }
}