/* ============================================
   28quan Design System — "Luminous Grid"
   Award-winning unique visual identity
   ============================================ */

@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@300;500;700;900&display=swap');

:root {
  --color-bg: #0b0d17;
  --color-surface: #14172b;
  --color-primary: #facc15;
  --color-primary-dim: #a3850e;
  --color-secondary: #06b6d4;
  --color-accent: #f97316;
  --color-text: #f1f5f9;
  --color-text-muted: #94a3b8;
  --color-border: rgba(250, 204, 21, 0.25);
  --color-glow: rgba(250, 204, 21, 0.15);
  --font-family: 'Noto Sans SC', -apple-system, 'Microsoft YaHei', sans-serif;
  --transition-fast: 0.25s cubic-bezier(0.25, 0.1, 0.25, 1);
  --transition-smooth: 0.45s cubic-bezier(0.22, 1, 0.36, 1);
  --radius: 0.75rem;
  --shadow-card: 0 10px 30px -10px rgba(0, 0, 0, 0.6), 0 0 0 1px rgba(250, 204, 21, 0.08);
  --shadow-glow: 0 0 30px var(--color-glow);
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-family);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

/* ---------- Container ---------- */
.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 2rem;
  position: relative;
}

/* ---------- Site Header ---------- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 1000;
  background: rgba(11, 13, 23, 0.75);
  backdrop-filter: blur(14px) saturate(180%);
  -webkit-backdrop-filter: blur(14px) saturate(180%);
  border-bottom: 1px solid var(--color-border);
  transition: background var(--transition-smooth), border-color var(--transition-smooth);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
  padding: 0 2rem;
  max-width: 1280px;
  margin: 0 auto;
}

.logo {
  font-size: 1.9rem;
  font-weight: 900;
  letter-spacing: -0.02em;
  color: var(--color-primary);
  text-transform: uppercase;
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  transition: transform var(--transition-fast);
}

.logo::before {
  content: "◆";
  font-size: 1.6rem;
  color: var(--color-accent);
  display: inline-block;
  animation: pulse-glow 2.5s infinite alternate;
}

.logo:hover {
  transform: scale(1.02);
  text-shadow: 0 0 20px var(--color-glow);
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 2.5rem;
  list-style: none;
}

.main-nav a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-weight: 500;
  font-size: 0.95rem;
  letter-spacing: 0.02em;
  position: relative;
  padding: 0.3rem 0;
  transition: color var(--transition-fast), transform var(--transition-fast);
}

.main-nav a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -2px;
  width: 0;
  height: 2px;
  background: var(--color-primary);
  transition: width var(--transition-smooth);
}

.main-nav a:hover {
  color: var(--color-primary);
  transform: translateY(-1px);
}

.main-nav a:hover::after {
  width: 100%;
}

.nav-cta {
  background: transparent;
  border: 1.5px solid var(--color-primary);
  color: var(--color-primary);
  padding: 0.55rem 1.6rem;
  border-radius: 50px;
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  cursor: pointer;
  transition: all var(--transition-fast);
  box-shadow: 0 0 0 transparent;
}

.nav-cta:hover {
  background: var(--color-primary);
  color: var(--color-bg);
  box-shadow: 0 0 25px var(--color-glow);
  transform: scale(1.04);
}

.menu-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--color-primary);
  font-size: 2rem;
  cursor: pointer;
  padding: 0.2rem;
  transition: transform var(--transition-fast);
}

.menu-toggle:hover {
  transform: rotate(90deg);
}

/* ---------- Hero ---------- */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 8rem 2rem 6rem;
  position: relative;
  overflow: hidden;
  background: radial-gradient(circle at 20% 30%, rgba(6, 182, 212, 0.12), transparent 50%),
              radial-gradient(circle at 80% 70%, rgba(250, 204, 21, 0.08), transparent 50%);
}

.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: 
    linear-gradient(0deg, transparent 24%, var(--color-border) 25%, var(--color-border) 26%, transparent 27%, transparent),
    linear-gradient(90deg, transparent 24%, var(--color-border) 25%, var(--color-border) 26%, transparent 27%, transparent);
  background-size: 80px 80px;
  opacity: 0.15;
  pointer-events: none;
}

.hero-content {
  max-width: 820px;
  text-align: center;
  position: relative;
  z-index: 2;
}

.hero-eyebrow {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--color-secondary);
  background: rgba(6, 182, 212, 0.12);
  padding: 0.4rem 1.4rem;
  border-radius: 50px;
  margin-bottom: 1.8rem;
  border: 1px solid rgba(6, 182, 212, 0.25);
  backdrop-filter: blur(4px);
}

.hero-content h1 {
  font-size: clamp(3.2rem, 12vw, 6.5rem);
  font-weight: 900;
  line-height: 1.05;
  letter-spacing: -0.03em;
  color: var(--color-text);
  margin-bottom: 1.2rem;
  text-shadow: 0 2px 30px rgba(0, 0, 0, 0.6);
}

.hero-content h1 span {
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-content p {
  font-size: 1.15rem;
  color: var(--color-text-muted);
  max-width: 600px;
  margin: 0 auto 2.5rem;
  line-height: 1.7;
}

.hero-buttons {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 1.2rem;
}

.hero-image {
  margin-top: 3rem;
  width: 100%;
  max-width: 700px;
  aspect-ratio: 16 / 9;
  background: radial-gradient(circle at 30% 40%, var(--color-primary-dim), transparent 70%);
  border-radius: var(--radius);
  box-shadow: var(--shadow-card), var(--shadow-glow);
  position: relative;
  overflow: hidden;
  border: 1px solid var(--color-border);
  transition: transform var(--transition-smooth), box-shadow var(--transition-smooth);
}

.hero-image:hover {
  transform: scale(1.01) translateY(-4px);
  box-shadow: var(--shadow-card), 0 0 50px var(--color-glow);
}

.hero-image::after {
  content: "28quan";
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3rem;
  font-weight: 900;
  color: rgba(255, 255, 255, 0.04);
  letter-spacing: 0.2em;
  text-transform: uppercase;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 2rem;
  border-radius: 50px;
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: 0.03em;
  text-decoration: none;
  cursor: pointer;
  transition: all var(--transition-fast);
  border: none;
  font-family: var(--font-family);
}

.btn-primary {
  background: var(--color-primary);
  color: var(--color-bg);
  box-shadow: 0 4px 15px rgba(250, 204, 21, 0.3);
}

.btn-primary:hover {
  background: #fde047;
  transform: translateY(-3px) scale(1.02);
  box-shadow: 0 10px 30px rgba(250, 204, 21, 0.4);
}

.btn-outline {
  background: transparent;
  color: var(--color-primary);
  border: 2px solid var(--color-primary);
}

.btn-outline:hover {
  background: var(--color-primary);
  color: var(--color-bg);
  transform: translateY(-3px);
  box-shadow: 0 0 25px var(--color-glow);
}

/* ---------- Section ---------- */
.section {
  padding: 5rem 0;
  position: relative;
}

.section-label {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.25em;
  text-transform: uppercase;
  color: var(--color-secondary);
  border-left: 4px solid var(--color-primary);
  padding-left: 0.8rem;
  margin-bottom: 1.2rem;
}

.section-title {
  font-size: clamp(2rem, 6vw, 3.8rem);
  font-weight: 900;
  line-height: 1.1;
  letter-spacing: -0.02em;
  margin-bottom: 1rem;
  color: var(--color-text);
}

.section-desc {
  font-size: 1.05rem;
  color: var(--color-text-muted);
  max-width: 600px;
  line-height: 1.7;
}

/* ---------- Cards Grid ---------- */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 2rem;
  margin-top: 3rem;
}

.category-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 2.2rem 1.8rem;
  transition: all var(--transition-smooth);
  position: relative;
  overflow: hidden;
  cursor: pointer;
}

.category-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 0;
  background: var(--color-primary);
  transition: height var(--transition-smooth);
}

.category-card:hover {
  transform: translateY(-8px);
  border-color: var(--color-primary);
  box-shadow: var(--shadow-card), var(--shadow-glow);
}

.category-card:hover::before {
  height: 100%;
}

.card-icon {
  font-size: 2.6rem;
  margin-bottom: 1rem;
  display: inline-block;
  color: var(--color-primary);
  filter: drop-shadow(0 0 8px var(--color-glow));
}

.category-card h3 {
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 0.7rem;
}

.category-card p {
  color: var(--color-text-muted);
  font-size: 0.9rem;
  line-height: 1.6;
}

.card-link {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--color-primary);
  font-weight: 700;
  font-size: 0.85rem;
  text-decoration: none;
  margin-top: 1.2rem;
  transition: gap var(--transition-fast);
}

.card-link:hover {
  gap: 1rem;
}

/* ---------- Feature Block ---------- */
.feature-block {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  align-items: center;
  margin: 4rem 0;
}

.feature-image {
  width: 100%;
  aspect-ratio: 4 / 3;
  background: linear-gradient(145deg, var(--color-surface), var(--color-bg));
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-card);
  position: relative;
  overflow: hidden;
  transition: transform var(--transition-smooth);
}

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

.feature-image::before {
  content: "◈";
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 5rem;
  color: rgba(250, 204, 21, 0.08);
}

.feature-text h3 {
  font-size: 1.8rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

.feature-list {
  list-style: none;
  margin-top: 1.5rem;
}

.feature-list li {
  display: flex;
  align-items: flex-start;
  gap: 0.8rem;
  margin-bottom: 0.8rem;
  color: var(--color-text-muted);
}

.feature-list li::before {
  content: "▸";
  color: var(--color-primary);
  font-weight: 700;
  font-size: 1.2rem;
}

/* ---------- Stats Bar ---------- */
.stats-bar {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-around;
  gap: 2rem;
  padding: 3rem 1rem;
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
  margin: 3rem 0;
}

.stat-item {
  text-align: center;
  flex: 1 1 140px;
}

.stat-number {
  font-size: 3rem;
  font-weight: 900;
  color: var(--color-primary);
  line-height: 1;
  display: block;
  letter-spacing: -0.02em;
  text-shadow: 0 0 20px var(--color-glow);
}

.stat-label {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-top: 0.4rem;
}

/* ---------- Content Wall (masonry-style) ---------- */
.content-wall {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
  margin: 3rem 0;
}

.content-wall-item {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 2rem;
  transition: all var(--transition-smooth);
  position: relative;
}

.content-wall-item:hover {
  border-color: var(--color-primary);
  transform: translateY(-4px);
  box-shadow: var(--shadow-card);
}

.content-wall-body {
  font-size: 0.95rem;
  color: var(--color-text-muted);
  line-height: 1.7;
}

.content-wall-item h4 {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 0.6rem;
  color: var(--color-text);
}

/* ---------- FAQ ---------- */
.faq-list {
  max-width: 780px;
  margin: 2.5rem auto 0;
}

.faq-item {
  border-bottom: 1px solid var(--color-border);
  padding: 1.2rem 0;
  cursor: pointer;
  transition: border-color var(--transition-fast);
}

.faq-item:hover {
  border-color: var(--color-primary);
}

.faq-item summary {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-text);
  display: flex;
  justify-content: space-between;
  align-items: center;
  list-style: none;
  transition: color var(--transition-fast);
}

.faq-item summary::-webkit-details-marker {
  display: none;
}

.faq-item summary::after {
  content: "+";
  font-size: 1.6rem;
  color: var(--color-primary);
  transition: transform var(--transition-smooth);
}

.faq-item[open] summary::after {
  transform: rotate(45deg);
}

.faq-answer {
  padding-top: 1rem;
  color: var(--color-text-muted);
  line-height: 1.7;
  font-size: 0.95rem;
}

/* ---------- CTA Banner ---------- */
.cta-banner {
  background: linear-gradient(135deg, var(--color-surface), #1e1b2e);
  border: 1px solid var(--color-border);
  border-radius: calc(var(--radius) * 1.5);
  padding: 4rem 3rem;
  text-align: center;
  margin: 4rem 0;
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow-card);
}

.cta-banner::before {
  content: "28";
  position: absolute;
  top: -20%;
  right: -5%;
  font-size: 18rem;
  font-weight: 900;
  color: rgba(250, 204, 21, 0.03);
  pointer-events: none;
  line-height: 1;
}

.cta-banner h2 {
  font-size: 2.2rem;
  font-weight: 900;
  margin-bottom: 1rem;
  position: relative;
}

.cta-banner p {
  color: var(--color-text-muted);
  max-width: 500px;
  margin: 0 auto 2rem;
  position: relative;
}

/* ---------- Footer ---------- */
.site-footer {
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: 4rem 2rem 2rem;
  margin-top: 5rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 2.5rem;
  max-width: 1280px;
  margin: 0 auto;
}

.footer-brand .logo {
  margin-bottom: 1rem;
  font-size: 1.6rem;
}

.footer-brand p {
  color: var(--color-text-muted);
  font-size: 0.9rem;
  max-width: 280px;
  line-height: 1.7;
}

.footer-col h4 {
  font-size: 0.9rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-primary);
  margin-bottom: 1.2rem;
}

.footer-col a {
  display: block;
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.85rem;
  padding: 0.3rem 0;
  transition: color var(--transition-fast), padding-left var(--transition-fast);
}

.footer-col a:hover {
  color: var(--color-primary);
  padding-left: 6px;
}

.footer-bottom {
  border-top: 1px solid rgba(250, 204, 21, 0.1);
  margin-top: 3rem;
  padding-top: 1.5rem;
  text-align: center;
  font-size: 0.8rem;
  color: var(--color-text-muted);
  max-width: 1280px;
  margin-left: auto;
  margin-right: auto;
}

/* ---------- Utility ---------- */
.text-accent {
  color: var(--color-primary);
}

.text-center {
  text-align: center;
}

.seo-description {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ---------- Animations ---------- */
@keyframes pulse-glow {
  0% { text-shadow: 0 0 5px var(--color-glow); }
  100% { text-shadow: 0 0 25px var(--color-primary), 0 0 50px var(--color-glow); }
}

/* ---------- Responsive ---------- */
@media (max-width: 1024px) {
  .feature-block {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

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

@media (max-width: 768px) {
  .container {
    padding: 0 1.2rem;
  }

  .header-inner {
    padding: 0 1.2rem;
  }

  .main-nav {
    position: fixed;
    top: 72px;
    left: 0;
    width: 100%;
    background: rgba(11, 13, 23, 0.98);
    backdrop-filter: blur(20px);
    flex-direction: column;
    padding: 2rem 1.5rem;
    gap: 1.5rem;
    transform: translateY(-120%);
    opacity: 0;
    transition: transform 0.4s cubic-bezier(0.22, 1, 0.36, 1), opacity 0.3s;
    border-bottom: 1px solid var(--color-border);
    pointer-events: none;
  }

  .main-nav.active {
    transform: translateY(0);
    opacity: 1;
    pointer-events: all;
  }

  .menu-toggle {
    display: block;
  }

  .hero {
    padding: 6rem 1.2rem 4rem;
  }

  .hero-content h1 {
    font-size: clamp(2.6rem, 10vw, 4rem);
  }

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

  .stats-bar {
    flex-direction: column;
    align-items: center;
  }

  .content-wall {
    grid-template-columns: 1fr;
  }

  .cta-banner {
    padding: 2.5rem 1.5rem;
  }

  .cta-banner h2 {
    font-size: 1.6rem;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .footer-brand p {
    margin: 0 auto;
  }
}

@media (max-width: 480px) {
  .hero-content h1 {
    font-size: 2.2rem;
  }

  .btn {
    padding: 0.6rem 1.4rem;
    font-size: 0.85rem;
  }

  .section-title {
    font-size: 1.8rem;
  }

  .stat-number {
    font-size: 2.4rem;
  }

  .cta-banner h2 {
    font-size: 1.3rem;
  }
}

/* ---------- Menu toggle JS helper (for demo, pure CSS fallback) ---------- */
.menu-toggle[aria-expanded="true"] + .main-nav,
.menu-toggle.active + .main-nav {
  transform: translateY(0);
  opacity: 1;
  pointer-events: all;
}