/* CourseHub - Online Course ROI Evaluation
   基础样式：深色主题 + 绿色强调（教育/成长主题）+ 响应式布局
   包含 ROI 卡片、计算器、对比表格样式 */

:root {
  --bg: #0a1a0a;
  --bg-alt: #0f172a;
  --bg-card: #111827;
  --text: #e5e7eb;
  --text-muted: #94a3b8;
  --border: #1f2937;
  --primary: #16a34a;
  --primary-hover: #15803d;
  --accent: #22c55e;
  --success: #22c55e;
  --warning: #f59e0b;
  --danger: #ef4444;
  --radius: 8px;
  --max-width: 1200px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --mono: "SF Mono", "Fira Code", Consolas, "Liberation Mono", Menlo, monospace;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

body.rtl { direction: rtl; }

a { color: var(--accent); text-decoration: none; transition: color .15s; }
a:hover { color: var(--primary); text-decoration: underline; }

img, svg { max-width: 100%; height: auto; }

.container { max-width: var(--max-width); margin: 0 auto; padding: 0 1rem; }

.sr-only, .skip-link {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}
.skip-link:focus { position: fixed; top: 0; left: 0; width: auto; height: auto; padding: .5rem 1rem; background: var(--primary); color: #fff; z-index: 9999; clip: auto; }

/* Header */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: rgba(10, 26, 10, .95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  padding: .75rem 1rem; gap: 1rem;
}
.logo {
  display: flex; align-items: center; gap: .5rem;
  font-weight: 700; font-size: 1.125rem; color: var(--text);
}
.logo:hover { text-decoration: none; }
.logo-text { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; max-width: 200px; }
.main-nav {
  display: flex; gap: 1.25rem; align-items: center;
}
.main-nav a {
  color: var(--text-muted); font-weight: 500; padding: .5rem 0;
  border-bottom: 2px solid transparent;
}
.main-nav a:hover, .main-nav a.active {
  color: var(--accent); border-bottom-color: var(--accent); text-decoration: none;
}
.header-actions {
  display: flex; align-items: center; gap: .75rem;
}
.menu-toggle {
  display: none; background: none; border: 0; cursor: pointer; padding: .5rem;
}
.menu-bar {
  display: block; width: 22px; height: 2px; background: var(--text);
  margin: 4px 0; transition: .2s;
}

/* Search box */
.search-box {
  display: flex; gap: .25rem; align-items: center;
}
.search-box input[type="search"] {
  background: var(--bg-card); border: 1px solid var(--border);
  color: var(--text); padding: .4rem .6rem; border-radius: 4px;
  font-size: .875rem; min-width: 180px;
}
.search-box button {
  background: var(--primary); color: #fff; border: 0;
  padding: .4rem .75rem; border-radius: 4px; cursor: pointer;
  font-size: .875rem;
}
.search-box button:hover { background: var(--primary-hover); }

/* Language switcher */
.language-switcher { position: relative; }
.lang-trigger {
  background: var(--bg-card); border: 1px solid var(--border); color: var(--text);
  padding: .4rem .6rem; border-radius: 4px; cursor: pointer;
  font-size: .875rem; display: flex; align-items: center; gap: .25rem;
}
.lang-menu {
  position: absolute; right: 0; top: calc(100% + 4px);
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: 4px; padding: .25rem 0; min-width: 160px;
  list-style: none; box-shadow: 0 8px 16px rgba(0,0,0,.4);
  display: none; max-height: 360px; overflow-y: auto; z-index: 50;
}
.language-switcher:hover .lang-menu,
.language-switcher:focus-within .lang-menu { display: block; }
.lang-menu a {
  display: block; padding: .35rem .75rem; color: var(--text);
  font-size: .875rem;
}
.lang-menu a:hover { background: var(--bg-alt); text-decoration: none; }
.lang-menu a.active { color: var(--accent); font-weight: 600; }

/* Main container */
main.container { padding: 1.5rem 1rem; min-height: 60vh; }

/* Home page */
.home-page { padding: 1rem 0; }
.home-header {
  text-align: center; padding: 2.5rem 1rem; margin-bottom: 2rem;
  background: linear-gradient(135deg, rgba(34, 197, 94, .08), rgba(14, 165, 233, .04));
  border-radius: 12px; border: 1px solid var(--border);
}
.home-header h1 { font-size: 2.25rem; color: var(--text); margin-bottom: .5rem; }
.home-tagline {
  color: var(--text-muted); font-size: 1.1rem; max-width: 720px; margin: 0 auto 1.5rem;
}
.home-search {
  max-width: 560px; margin: 0 auto 1.5rem;
}
.home-search .search-box input { width: 100%; min-width: auto; }
.home-stats {
  display: flex; gap: 2rem; justify-content: center; flex-wrap: wrap;
}
.stat-item { display: flex; flex-direction: column; align-items: center; }
.stat-value {
  font-size: 1.75rem; font-weight: 700; color: var(--accent);
}
.stat-label { color: var(--text-muted); font-size: .875rem; }

.home-section { margin: 2.5rem 0; }
.home-section h2 {
  font-size: 1.5rem; margin-bottom: 1rem; color: var(--text);
  border-bottom: 1px solid var(--border); padding-bottom: .5rem;
}

/* Card grid */
.card-grid {
  display: grid; gap: 1rem;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
}
.card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1rem 1.25rem;
  transition: border-color .15s, transform .15s;
}
.card:hover {
  border-color: var(--accent); transform: translateY(-2px);
}
.card-link {
  display: block; color: inherit;
}
.card-link:hover { text-decoration: none; }
.card-title {
  font-size: 1.05rem; margin-bottom: .35rem; color: var(--accent);
}
.card-description {
  color: var(--text-muted); font-size: .875rem;
  display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical;
  overflow: hidden; margin-bottom: .5rem;
}
.card-meta {
  font-size: .75rem; color: var(--text-muted);
  display: flex; gap: .25rem; align-items: center;
}
.meta-separator { opacity: .6; }

/* List page */
.list-page { padding: 1rem 0; }
.breadcrumb ol {
  list-style: none; display: flex; gap: .35rem; flex-wrap: wrap;
  font-size: .875rem; color: var(--text-muted); margin-bottom: 1rem;
}
.breadcrumb li::after { content: " ›"; margin-left: .35rem; color: var(--border); }
.breadcrumb li:last-child::after { content: ""; }
.breadcrumb li[aria-current="page"] { color: var(--text); }

.list-header { margin-bottom: 1.5rem; }
.list-header h1 { font-size: 1.875rem; margin-bottom: .5rem; }
.list-description { color: var(--text-muted); margin-bottom: .75rem; }
.list-meta {
  display: flex; justify-content: space-between; align-items: center;
  font-size: .875rem; color: var(--text-muted); flex-wrap: wrap; gap: .5rem;
}

/* Single page */
.single-detail { padding: 1rem 0 2rem; }
.single-header { margin-bottom: 1.5rem; }
.single-header h1 { font-size: 2rem; margin-bottom: .5rem; }
.list-description { font-size: 1rem; }
.single-meta {
  font-size: .875rem; color: var(--text-muted);
  display: flex; gap: .25rem; align-items: center; flex-wrap: wrap;
}
.single-content {
  font-size: 1rem; line-height: 1.7; color: var(--text);
  margin-bottom: 2rem;
}
.single-content h2 {
  font-size: 1.5rem; margin: 1.5rem 0 .75rem; color: var(--text);
  border-bottom: 1px solid var(--border); padding-bottom: .35rem;
}
.single-content h3 {
  font-size: 1.2rem; margin: 1.25rem 0 .5rem; color: var(--text);
}
.single-content p { margin-bottom: 1rem; }
.single-content ul, .single-content ol { margin: 0 0 1rem 1.5rem; }
.single-content li { margin-bottom: .35rem; }
.single-content code {
  background: var(--bg-card); padding: .15rem .35rem; border-radius: 3px;
  font-family: var(--mono); font-size: .9em;
}
.single-content pre {
  background: var(--bg-card); padding: 1rem; border-radius: 6px;
  overflow-x: auto; margin-bottom: 1rem;
}
.single-content table {
  width: 100%; border-collapse: collapse; margin-bottom: 1rem;
}
.single-content th, .single-content td {
  border: 1px solid var(--border); padding: .5rem .75rem;
  text-align: left;
}
.single-content th { background: var(--bg-card); color: var(--text); }

/* ROI card */
.roi-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.25rem;
  margin: 1.5rem 0;
}
.roi-card h2 {
  font-size: 1.2rem; margin-bottom: 1rem; color: var(--accent);
}
.roi-grid {
  display: grid; gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
}
.roi-item {
  display: flex; flex-direction: column; align-items: center;
  padding: .75rem; background: var(--bg-alt);
  border-radius: 6px; text-align: center;
}
.roi-label {
  font-size: .75rem; color: var(--text-muted); margin-bottom: .25rem;
  text-transform: uppercase; letter-spacing: .05em;
}
.roi-value {
  font-size: 1.5rem; font-weight: 700; color: var(--text);
}
.roi-value.roi-score { color: var(--accent); }

/* Tags */
.single-tags { margin: 1.5rem 0; }
.tags-title { font-size: 1rem; margin-bottom: .5rem; color: var(--text); }
.tags-inline { list-style: none; display: flex; gap: .35rem; flex-wrap: wrap; }
.tag-pill {
  display: inline-block; padding: .2rem .6rem;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: 999px; font-size: .75rem; color: var(--accent);
}
.tag-pill:hover { border-color: var(--accent); }

/* Related links */
.related-links { margin: 1.5rem 0; }
.related-links h2 { font-size: 1.1rem; margin-bottom: .5rem; }
.compare-inline { list-style: none; display: flex; gap: .35rem; flex-wrap: wrap; }

/* Other languages */
.single-languages { margin: 2rem 0; padding-top: 1rem; border-top: 1px solid var(--border); }
.single-languages h2 { font-size: 1rem; margin-bottom: .5rem; color: var(--text-muted); }

/* Post navigation */
.post-nav {
  display: flex; justify-content: space-between; gap: 1rem;
  margin-top: 2rem; padding-top: 1.5rem; border-top: 1px solid var(--border);
}
.post-nav-prev, .post-nav-next {
  flex: 1; display: flex; flex-direction: column; gap: .25rem;
}
.post-nav-next { text-align: right; }
.post-nav-empty { visibility: hidden; }
.post-nav-label { font-size: .75rem; color: var(--text-muted); text-transform: uppercase; }
.post-nav-title { font-size: .875rem; color: var(--accent); }

/* Pagination */
.pagination {
  display: flex; justify-content: center; align-items: center;
  gap: 1rem; margin: 1.5rem 0;
}
.page-info { color: var(--text-muted); font-size: .875rem; }
.page-prev, .page-next {
  padding: .35rem .75rem; background: var(--bg-card);
  border: 1px solid var(--border); border-radius: 4px;
  color: var(--text); font-size: .875rem;
}
.page-prev:hover, .page-next:hover { border-color: var(--accent); text-decoration: none; }

/* Calculator */
.calc-container {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.5rem; margin: 1.5rem 0;
}
.calc-container h2 { color: var(--accent); margin-bottom: .5rem; }
.calc-intro { color: var(--text-muted); margin-bottom: 1rem; }
.calc-form {
  display: grid; gap: .75rem;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  margin-bottom: 1rem;
}
.form-row {
  display: flex; flex-direction: column; gap: .25rem;
}
.form-row label {
  font-size: .8rem; color: var(--text-muted);
}
.form-row input {
  background: var(--bg-alt); border: 1px solid var(--border);
  color: var(--text); padding: .5rem .75rem; border-radius: 4px;
  font-size: .95rem;
}
.form-row input:focus {
  outline: none; border-color: var(--accent);
}
.btn {
  padding: .55rem 1rem; border-radius: 4px; border: 0;
  cursor: pointer; font-size: .875rem; font-weight: 500;
  display: inline-flex; align-items: center; justify-content: center; gap: .35rem;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-hover); }
.btn-secondary { background: var(--bg-alt); color: var(--text); border: 1px solid var(--border); }
.calc-result {
  margin-top: 1.5rem; padding: 1rem; background: var(--bg-alt);
  border-radius: 6px; border: 1px solid var(--accent);
}
.calc-result h3 { color: var(--accent); margin-bottom: .75rem; }
.result-grid {
  display: grid; gap: .75rem;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
}
.result-item {
  display: flex; flex-direction: column; align-items: center;
  text-align: center;
}
.result-label {
  font-size: .75rem; color: var(--text-muted); text-transform: uppercase;
  letter-spacing: .05em; margin-bottom: .25rem;
}
.result-value {
  font-size: 1.25rem; font-weight: 700; color: var(--text);
}
.result-value.roi-score { color: var(--accent); }

/* 404 page */
.not-found-page {
  display: flex; align-items: center; justify-content: center;
  min-height: 60vh; text-align: center;
}
.not-found-code {
  font-size: 6rem; font-weight: 700; color: var(--accent);
  line-height: 1;
}
.not-found-title {
  font-size: 1.5rem; color: var(--text); margin: 1rem 0 .5rem;
}
.not-found-desc { color: var(--text-muted); margin-bottom: 1.5rem; }
.not-found-actions {
  display: flex; gap: .5rem; justify-content: center; flex-wrap: wrap; margin-bottom: 1.5rem;
}
.not-found-search { max-width: 480px; margin: 0 auto; }
.not-found-search .search-box input { width: 100%; }

/* Footer */
.site-footer {
  background: var(--bg-alt); border-top: 1px solid var(--border);
  padding: 2.5rem 1rem 1.5rem; margin-top: 3rem;
}
.footer-grid {
  display: grid; gap: 2rem;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  margin-bottom: 1.5rem;
}
.footer-col h4 {
  font-size: .95rem; margin-bottom: .75rem; color: var(--text);
}
.footer-col ul { list-style: none; }
.footer-col li { margin-bottom: .35rem; }
.footer-col a { color: var(--text-muted); font-size: .875rem; }
.footer-col a:hover { color: var(--accent); }
.footer-brand p { color: var(--text-muted); font-size: .875rem; }
.footer-langs {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: .25rem;
}
.footer-langs li { margin: 0; }
.footer-disclaimer {
  font-size: .75rem; color: var(--text-muted);
  border-top: 1px solid var(--border); padding-top: 1rem; margin-bottom: 1rem;
}
.footer-bottom {
  text-align: center; color: var(--text-muted); font-size: .8rem;
  padding-top: 1rem; border-top: 1px solid var(--border);
}

/* Empty state */
.empty-state {
  text-align: center; padding: 3rem 1rem; color: var(--text-muted);
}

/* Responsive */
@media (max-width: 768px) {
  .main-nav { display: none; }
  .menu-toggle { display: block; }
  .main-nav.is-open {
    display: flex; flex-direction: column; position: absolute;
    top: 100%; left: 0; right: 0; background: var(--bg);
    border-bottom: 1px solid var(--border); padding: 1rem;
  }
  .main-nav.is-open a { padding: .75rem 0; }
  .header-actions { flex: 1; }
  .search-box input { min-width: 120px; }
  .home-stats { gap: 1rem; }
  .stat-value { font-size: 1.4rem; }
  .footer-langs { grid-template-columns: repeat(2, 1fr); }
  .post-nav { flex-direction: column; gap: 1rem; }
  .post-nav-next { text-align: left; }
}

/* RTL */
body.rtl .breadcrumb li::after { content: " ‹"; }
body.rtl .post-nav-next { text-align: left; }