/* ============================================================
   CSS VARIABLES – THEMES
============================================================ */
:root {
  --pink-primary: #f2587a;
  --pink-light: #ff8fab;
  --pink-muted: #ffe4ec;
  --pink-glow: rgba(242, 88, 122, 0.18);
  --radius-lg: 20px;
  --radius-md: 12px;
  --radius-sm: 8px;
  --shadow-card: 0 8px 32px rgba(0,0,0,0.18);
  --shadow-hover: 0 16px 48px rgba(242, 88, 122, 0.22);
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --max-width: 1200px;
  --font-display: 'Playfair Display', serif;
  --font-body: 'DM Sans', sans-serif;
}

/* Dark mode (default) */
[data-theme="dark"] {
  --bg: #141118;
  --bg-surface: #1e1926;
  --bg-card: #231d2e;
  --bg-header: rgba(20, 17, 24, 0.85);
  --text-primary: #f2edf8;
  --text-secondary: #a898b8;
  --text-muted: #6e6080;
  --border: rgba(255,255,255,0.07);
  --tag-bg: rgba(242, 88, 122, 0.15);
  --footer-bg: #0e0c14;
}

/* Light mode */
[data-theme="light"] {
  --bg: #fdf6f9;
  --bg-surface: #fff0f5;
  --bg-card: #ffffff;
  --bg-header: rgba(253, 246, 249, 0.88);
  --text-primary: #1a0f1e;
  --text-secondary: #6b4a6e;
  --text-muted: #a890b0;
  --border: rgba(0,0,0,0.07);
  --tag-bg: rgba(242, 88, 122, 0.1);
  --footer-bg: #f0e6f0;
}

/* ============================================================
   RESET & BASE
============================================================ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; max-width: 100%; }

html {
  scroll-behavior: smooth;
  overflow-x: hidden;
}

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text-primary);
  line-height: 1.7;
  overflow-x: hidden;
  max-width: 100%;
  transition: background var(--transition), color var(--transition);
}

a { color: inherit; text-decoration: none; }

img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-md);
}

/* ============================================================
   SKIP TO CONTENT – Accessibility
============================================================ */
.skip-link {
  position: absolute;
  top: -100px;
  left: 16px;
  background: var(--pink-primary);
  color: #fff;
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 600;
  z-index: 9999;
  transition: top 0.2s;
}
.skip-link:focus { top: 8px; }

/* ============================================================
   HEADER
============================================================ */
header {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  background: var(--bg-header);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  transition: background var(--transition), box-shadow var(--transition);
}

header.scrolled {
  box-shadow: 0 4px 24px rgba(0,0,0,0.18);
}

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

/* Logo */
.logo-group {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}

.logo-icon {
  width: 40px; height: 40px;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--pink-primary), #a855f7);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  box-shadow: 0 4px 14px rgba(242, 88, 122, 0.4);
}

.logo-icon svg { width: 22px; height: 22px; }

.logo {
  font-family: var(--font-display);
  font-size: 1.4rem;
  font-weight: 900;
  letter-spacing: -0.5px;
  background: linear-gradient(135deg, var(--pink-primary), var(--pink-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* Header right */
.header-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

/* Dark / Light toggle */
.theme-toggle {
  width: 52px; height: 28px;
  background: var(--bg-surface);
  border: 2px solid var(--border);
  border-radius: 99px;
  cursor: pointer;
  position: relative;
  transition: background var(--transition), border-color var(--transition);
  flex-shrink: 0;
  overflow: hidden;
}

.theme-toggle::before {
  content: '🌙';
  position: absolute;
  top: 3px; left: 3px;
  width: 18px; height: 18px;
  background: linear-gradient(135deg, var(--pink-primary), var(--pink-light));
  border-radius: 50%;
  transition: transform var(--transition);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 10px;
  line-height: 18px;
  text-align: center;
}

[data-theme="light"] .theme-toggle::before {
  content: '☀️';
  transform: translateX(24px);
}

.toggle-icons { display: none; }
.hamburger { display: none !important; }

/* ============================================================
   MAIN LAYOUT
============================================================ */
.page-wrapper {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 100px 24px 60px;
}

.content-grid {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 40px;
  align-items: start;
}

/* ============================================================
   BREADCRUMB
============================================================ */
.breadcrumb {
  margin-bottom: 28px;
}

.breadcrumb ol {
  list-style: none;
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
}

.breadcrumb li {
  font-size: 0.82rem;
  color: var(--text-muted);
}

.breadcrumb a {
  color: var(--text-muted);
  transition: color var(--transition);
}

.breadcrumb a:hover { color: var(--pink-primary); }

.breadcrumb span[aria-hidden] {
  color: var(--text-muted);
  font-size: 0.78rem;
}

.breadcrumb li:last-child {
  color: var(--pink-primary);
  font-weight: 500;
}

/* ============================================================
   ARTICLE HERO
============================================================ */
.article-hero {
  margin-bottom: 40px;
}

.article-category {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--pink-primary);
  background: var(--tag-bg);
  padding: 6px 14px;
  border-radius: 99px;
  margin-bottom: 20px;
}

.article-title {
  font-family: var(--font-display);
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 900;
  line-height: 1.15;
  letter-spacing: -1px;
  color: var(--text-primary);
  margin-bottom: 24px;
}

.article-title .highlight {
  background: linear-gradient(135deg, var(--pink-primary), var(--pink-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
  margin-bottom: 32px;
}

.meta-author {
  display: flex;
  align-items: center;
  gap: 10px;
}

.author-avatar {
  width: 38px; height: 38px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--pink-primary), #a855f7);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
  font-weight: 700;
  color: #fff;
  flex-shrink: 0;
}

.meta-author-name {
  font-weight: 600;
  font-size: 0.9rem;
}

.meta-divider {
  width: 4px; height: 4px;
  border-radius: 50%;
  background: var(--text-muted);
}

.meta-info {
  font-size: 0.85rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 6px;
}

.meta-info svg { flex-shrink: 0; }

.cover-image {
  position: relative;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-card);
}

.cover-image img {
  border-radius: var(--radius-lg);
  transition: transform 0.6s ease;
  aspect-ratio: 16/9;
  object-fit: cover;
}

.cover-image:hover img { transform: scale(1.02); }

/* ============================================================
   ARTICLE BODY
============================================================ */
.article-body {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: 48px;
  border: 1px solid var(--border);
  box-shadow: var(--shadow-card);
}

.intro-text {
  font-size: 1.15rem;
  color: var(--text-secondary);
  line-height: 1.85;
  border-left: 3px solid var(--pink-primary);
  padding-left: 20px;
  margin-bottom: 48px;
  font-style: italic;
}

/* Sections */
.blog-section {
  margin-bottom: 56px;
  opacity: 0;
  transform: translateY(28px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

.blog-section.visible {
  opacity: 1;
  transform: translateY(0);
}

.section-number {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--pink-primary);
  margin-bottom: 8px;
}

.section-title {
  font-family: var(--font-display);
  font-size: 1.7rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 18px;
  line-height: 1.3;
}

.section-text {
  color: var(--text-secondary);
  font-size: 1rem;
  line-height: 1.9;
  margin-bottom: 28px;
}

.section-text strong { color: var(--text-primary); font-weight: 600; }

/* Figure */
figure {
  margin: 28px 0;
  border-radius: var(--radius-lg);
  overflow: hidden;
  position: relative;
  box-shadow: var(--shadow-card);
}

figure img {
  border-radius: var(--radius-lg);
  transition: transform 0.5s ease;
  object-fit: cover;
  aspect-ratio: 16/9;
}

figure:hover img { transform: scale(1.03); }

figcaption {
  text-align: center;
  font-size: 0.82rem;
  color: var(--text-muted);
  padding: 12px 16px;
  background: var(--bg-surface);
  font-style: italic;
}

/* Highlight box */
.highlight-box {
  background: linear-gradient(135deg, var(--tag-bg), transparent);
  border: 1px solid rgba(242, 88, 122, 0.25);
  border-radius: var(--radius-md);
  padding: 24px 28px;
  margin: 28px 0;
}

.highlight-box p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.8;
}

.highlight-box p::before {
  content: '✦ ';
  color: var(--pink-primary);
  font-size: 0.8rem;
}

/* ============================================================
   SIDEBAR
============================================================ */
.sidebar {
  position: sticky;
  top: 84px;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.sidebar-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-card);
  opacity: 0;
  transform: translateX(20px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

.sidebar-card.visible {
  opacity: 1;
  transform: translateX(0);
}

.sidebar-card-title {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 18px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--pink-primary);
  display: flex;
  align-items: center;
  gap: 8px;
}

/* Related posts */
.related-post {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
  cursor: pointer;
  transition: transform var(--transition);
  text-decoration: none;
}

.related-post:last-child { border-bottom: none; padding-bottom: 0; }
.related-post:first-of-type { padding-top: 0; }
.related-post:hover { transform: translateX(4px); }

.related-thumb {
  width: 64px; height: 64px;
  border-radius: var(--radius-sm);
  overflow: hidden;
  flex-shrink: 0;
}

.related-thumb img {
  width: 100%; height: 100%;
  object-fit: cover;
  border-radius: var(--radius-sm);
  transition: transform 0.4s ease;
}

.related-post:hover .related-thumb img { transform: scale(1.1); }

.related-info { flex: 1; }

.related-title {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.4;
  margin-bottom: 4px;
  transition: color var(--transition);
}

.related-post:hover .related-title { color: var(--pink-primary); }

.related-date {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Categories */
.category-list { list-style: none; }

.category-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 0;
  border-bottom: 1px solid var(--border);
  cursor: pointer;
  transition: color var(--transition);
  font-size: 0.9rem;
  color: var(--text-secondary);
  text-decoration: none;
}

.category-item:last-child { border-bottom: none; }
.category-item:hover { color: var(--pink-primary); }

.category-count {
  font-size: 0.75rem;
  background: var(--tag-bg);
  color: var(--pink-primary);
  padding: 2px 8px;
  border-radius: 99px;
  font-weight: 600;
}

/* Tags */
.tags-cloud {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tag {
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 600;
  background: var(--tag-bg);
  color: var(--pink-primary);
  border: 1px solid rgba(242, 88, 122, 0.2);
  padding: 5px 14px;
  border-radius: 99px;
  cursor: pointer;
  transition: background var(--transition), color var(--transition), transform var(--transition);
}

.tag:hover {
  background: var(--pink-primary);
  color: #fff;
  transform: scale(1.05);
}

/* ============================================================
   FOOTER
============================================================ */
footer {
  background: var(--footer-bg);
  border-top: 1px solid var(--border);
  padding: 64px 24px 32px;
  margin-top: 80px;
}

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

.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand .logo { margin-bottom: 12px; }

.footer-brand p {
  font-size: 0.88rem;
  color: var(--text-muted);
  line-height: 1.7;
  max-width: 280px;
}

.footer-col-title {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 18px;
}

.footer-links { list-style: none; }

.footer-links li { margin-bottom: 10px; }

.footer-links a {
  font-size: 0.88rem;
  color: var(--text-muted);
  transition: color var(--transition);
  display: flex;
  align-items: center;
  gap: 6px;
}

.footer-links a:hover { color: var(--pink-primary); }

.social-links {
  display: flex;
  gap: 12px;
  margin-top: 4px;
}

.social-btn {
  width: 40px; height: 40px;
  border-radius: 50%;
  background: var(--bg-card);
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: background var(--transition), border-color var(--transition), transform var(--transition);
  font-size: 1.1rem;
  text-decoration: none;
}

.social-btn:hover {
  background: var(--pink-primary);
  border-color: var(--pink-primary);
  transform: translateY(-3px);
}

.footer-bottom {
  border-top: 1px solid var(--border);
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}

.footer-bottom p {
  font-size: 0.82rem;
  color: var(--text-muted);
}

.footer-bottom span { color: var(--pink-primary); }

/* ============================================================
   SCROLLBAR
============================================================ */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--pink-primary); border-radius: 99px; }

/* ============================================================
   UTILITY – ANIMATIONS
============================================================ */
.fade-in {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}
.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Loading skeleton */
.skeleton {
  background: linear-gradient(90deg, var(--bg-surface) 25%, var(--bg-card) 50%, var(--bg-surface) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius-sm);
}

@keyframes shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* ============================================================
   RESPONSIVE – TABLET (≤ 1024px)
============================================================ */
@media (max-width: 1024px) {
  .page-wrapper { padding: 90px 20px 56px; }

  .content-grid {
    grid-template-columns: 1fr 280px;
    gap: 28px;
  }

  .article-body { padding: 36px 32px; }

  .article-title {
    font-size: clamp(1.8rem, 4vw, 2.6rem);
    letter-spacing: -0.5px;
  }

  .footer-grid {
    grid-template-columns: 1.2fr 1fr 1fr;
    gap: 32px;
  }

  .section-title { font-size: 1.4rem; }
}

/* ============================================================
   RESPONSIVE – TABLET NHỎ (≤ 900px)
============================================================ */
@media (max-width: 900px) {
  .content-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .sidebar {
    position: static;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
  }

  .sidebar .sidebar-card:last-child { grid-column: 1 / -1; }

  .article-body { padding: 32px 28px; }

  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }

  .footer-brand {
    grid-column: 1 / -1;
  }

  .footer-brand p { max-width: 100%; }
}

/* ============================================================
   RESPONSIVE – MOBILE LỚN (≤ 640px)
============================================================ */
@media (max-width: 640px) {
  .page-wrapper { padding: 80px 16px 48px; }

  .header-inner { padding: 0 16px; height: 56px; }

  .logo { font-size: 1.15rem; }

  .logo-icon { width: 34px; height: 34px; border-radius: 8px; }
  .logo-icon svg { width: 18px; height: 18px; }

  .breadcrumb ol { gap: 4px; }
  .breadcrumb li { font-size: 0.75rem; }

  .article-hero { margin-bottom: 28px; }

  .article-title {
    font-size: clamp(1.6rem, 7vw, 2rem);
    letter-spacing: -0.5px;
    line-height: 1.2;
    margin-bottom: 18px;
  }

  .article-meta { gap: 12px; margin-bottom: 24px; }
  .meta-divider { display: none; }
  .author-avatar { width: 32px; height: 32px; font-size: 0.75rem; }
  .meta-author-name { font-size: 0.82rem; }
  .meta-info { font-size: 0.78rem; }

  .article-body { padding: 24px 18px; border-radius: var(--radius-md); }

  .intro-text { font-size: 1rem; padding-left: 14px; margin-bottom: 32px; }

  .section-title { font-size: 1.25rem; line-height: 1.35; }

  .section-text { font-size: 0.95rem; line-height: 1.8; margin-bottom: 20px; }

  .highlight-box { padding: 16px 18px; margin: 20px 0; }
  .highlight-box p { font-size: 0.88rem; }

  figure { margin: 20px 0; border-radius: var(--radius-md); }
  figure img { border-radius: var(--radius-md); }
  figcaption { font-size: 0.78rem; padding: 10px 12px; }

  .blog-section { margin-bottom: 36px; }

  .sidebar {
    display: flex;
    flex-direction: column;
    gap: 20px;
  }

  .sidebar-card { padding: 18px; border-radius: var(--radius-md); transform: none; }

  .related-thumb { width: 56px; height: 56px; }
  .related-title { font-size: 0.82rem; }

  footer { padding: 40px 16px 24px; margin-top: 48px; }

  .footer-grid { grid-template-columns: 1fr; gap: 28px; margin-bottom: 28px; }
  .footer-brand { grid-column: auto; }
  .footer-brand p { font-size: 0.84rem; }
  .footer-col-title { font-size: 0.95rem; margin-bottom: 12px; }
  .footer-links a { font-size: 0.84rem; }
  .footer-bottom { flex-direction: column; text-align: center; gap: 8px; }
  .social-links { gap: 8px; }
  .social-btn { width: 36px; height: 36px; font-size: 1rem; }
}

/* ============================================================
   RESPONSIVE – MOBILE NHỎ (≤ 390px)
============================================================ */
@media (max-width: 390px) {
  .page-wrapper { padding: 76px 12px 40px; }
  .article-title { font-size: 1.45rem; }
  .article-body { padding: 20px 14px; }
  .section-title { font-size: 1.15rem; }
  .logo { font-size: 1.05rem; }
  .article-meta { flex-direction: column; align-items: flex-start; gap: 8px; }
  .tags-cloud { gap: 6px; }
  .tag { font-size: 0.72rem; padding: 4px 10px; }
}