/* ============================================
   HKVS.org — Hong Kong Vertical Space Research Institute
   Design: Dark Aerospace Theme
   ============================================ */

/* ---------- CSS Variables ---------- */
:root {
  --bg-primary: #0D1B2A;
  --bg-secondary: #1B2838;
  --bg-card: #162232;
  --bg-glass: rgba(27, 40, 56, 0.7);
  --blue: #1E90FF;
  --blue-glow: rgba(30, 144, 255, 0.3);
  --teal: #00D4AA;
  --teal-glow: rgba(0, 212, 170, 0.2);
  --text-primary: #E8ECF1;
  --text-secondary: #8892A0;
  --text-muted: #5A6577;
  --border: rgba(255, 255, 255, 0.06);
  --gradient-hero: linear-gradient(135deg, #0D1B2A 0%, #152238 50%, #0a1520 100%);
  --gradient-blue: linear-gradient(135deg, #1E90FF, #00D4AA);
  --gradient-card: linear-gradient(180deg, rgba(30, 144, 255, 0.08) 0%, transparent 100%);
  --shadow-lg: 0 20px 60px rgba(0, 0, 0, 0.4);
  --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.3);
  --radius: 16px;
  --radius-sm: 8px;
  --nav-height: 72px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --font-en: 'Inter', 'Segoe UI', sans-serif;
  --font-zh: 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
}

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

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

body {
  font-family: var(--font-en);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

body.zh {
  font-family: var(--font-zh);
}

a {
  color: var(--blue);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--teal);
}

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

ul {
  list-style: none;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ---------- Utilities ---------- */
.section {
  padding: 100px 0;
}

.section-label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 3px;
  color: var(--teal);
  font-weight: 600;
  margin-bottom: 16px;
}

.section-label::before {
  content: '';
  width: 24px;
  height: 2px;
  background: var(--teal);
  border-radius: 1px;
}

.section-title {
  font-size: clamp(2rem, 4vw, 2.8rem);
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 20px;
}

.section-subtitle {
  font-size: 1.1rem;
  color: var(--text-secondary);
  max-width: 640px;
  line-height: 1.8;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 32px;
  border-radius: 50px;
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  border: none;
  transition: all var(--transition);
  text-decoration: none;
}

.btn-primary {
  background: var(--gradient-blue);
  color: #fff;
  box-shadow: 0 4px 20px var(--blue-glow);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px var(--blue-glow);
  color: #fff;
}

.btn-outline {
  background: transparent;
  color: var(--text-primary);
  border: 1.5px solid rgba(255, 255, 255, 0.2);
}

.btn-outline:hover {
  border-color: var(--blue);
  color: var(--blue);
  background: rgba(30, 144, 255, 0.05);
}

.gradient-text {
  background: var(--gradient-blue);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* ---------- Navigation ---------- */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: var(--nav-height);
  background: rgba(13, 27, 42, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  transition: all var(--transition);
}

.nav.scrolled {
  background: rgba(13, 27, 42, 0.95);
  box-shadow: var(--shadow-card);
}

.nav .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 12px;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text-primary);
  text-decoration: none;
}

.nav-logo .logo-icon {
  width: 36px;
  height: 36px;
  border-radius: 8px;
  background: var(--gradient-blue);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 0.85rem;
  color: #fff;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-links a {
  padding: 8px 18px;
  border-radius: 8px;
  font-size: 0.9rem;
  color: var(--text-secondary);
  font-weight: 500;
  transition: all var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--text-primary);
  background: rgba(255, 255, 255, 0.05);
}

.nav-lang {
  padding: 6px 14px;
  border-radius: 20px;
  font-size: 0.8rem;
  border: 1px solid rgba(255, 255, 255, 0.15);
  background: transparent;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition);
}

.nav-lang:hover {
  border-color: var(--blue);
  color: var(--blue);
}

.nav-mobile-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 1.5rem;
  cursor: pointer;
}

/* ---------- Hero Section ---------- */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  background: var(--gradient-hero);
  overflow: hidden;
  padding-top: var(--nav-height);
}

.hero-bg {
  position: absolute;
  inset: 0;
  background: url('../img/hero-bg.jpg') center/cover no-repeat;
  opacity: 0.15;
}

.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(30, 144, 255, 0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(30, 144, 255, 0.03) 1px, transparent 1px);
  background-size: 60px 60px;
}

.hero-glow {
  position: absolute;
  width: 600px;
  height: 600px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--blue-glow) 0%, transparent 70%);
  top: 20%;
  right: -10%;
  filter: blur(80px);
  animation: float 8s ease-in-out infinite;
}

.hero-glow-2 {
  position: absolute;
  width: 400px;
  height: 400px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--teal-glow) 0%, transparent 70%);
  bottom: 10%;
  left: -5%;
  filter: blur(60px);
  animation: float 10s ease-in-out infinite reverse;
}

@keyframes float {

  0%,
  100% {
    transform: translateY(0);
  }

  50% {
    transform: translateY(-30px);
  }
}

.hero .container {
  position: relative;
  z-index: 2;
}

.hero-content {
  max-width: 720px;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 20px;
  border-radius: 50px;
  background: rgba(30, 144, 255, 0.1);
  border: 1px solid rgba(30, 144, 255, 0.2);
  font-size: 0.8rem;
  color: var(--blue);
  font-weight: 600;
  letter-spacing: 1px;
  text-transform: uppercase;
  margin-bottom: 28px;
}

.hero-badge::before {
  content: '';
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--teal);
  animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {

  0%,
  100% {
    opacity: 1;
  }

  50% {
    opacity: 0.3;
  }
}

.hero h1 {
  font-size: clamp(2.5rem, 5vw, 3.8rem);
  font-weight: 800;
  line-height: 1.15;
  margin-bottom: 12px;
  letter-spacing: -0.5px;
  text-wrap: balance;
  max-width: 680px;
}

.hero h1 .zh-name {
  display: block;
  font-size: clamp(1.2rem, 2.5vw, 1.6rem);
  color: var(--text-secondary);
  font-weight: 400;
  margin-top: 8px;
  letter-spacing: 4px;
}

.hero-tagline {
  font-size: 1.2rem;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 40px;
  max-width: 560px;
}

.hero-actions {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

/* ---------- Stats Bar ---------- */
.stats-bar {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  padding: 48px 0;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 32px;
  text-align: center;
}

.stat-item .stat-number {
  font-size: 2.5rem;
  font-weight: 800;
  background: var(--gradient-blue);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-item .stat-label {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-top: 4px;
  text-transform: uppercase;
  letter-spacing: 1px;
}

/* ---------- Pillars / Services ---------- */
.pillars-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
  margin-top: 56px;
}

.pillar-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px 32px;
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.pillar-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--gradient-blue);
  opacity: 0;
  transition: opacity var(--transition);
}

.pillar-card:hover {
  transform: translateY(-4px);
  border-color: rgba(30, 144, 255, 0.2);
  box-shadow: var(--shadow-lg);
}

.pillar-card:hover::before {
  opacity: 1;
}

.pillar-icon {
  width: 56px;
  height: 56px;
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.6rem;
  margin-bottom: 24px;
}

.pillar-icon.research {
  background: rgba(30, 144, 255, 0.12);
  color: var(--blue);
}

.pillar-icon.tech {
  background: rgba(0, 212, 170, 0.12);
  color: var(--teal);
}

.pillar-icon.edu {
  background: rgba(255, 165, 0, 0.12);
  color: #FFA500;
}

.pillar-card h3 {
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.pillar-card p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.8;
  margin-bottom: 20px;
}

.pillar-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.pillar-list li {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.pillar-list li::before {
  content: '→';
  color: var(--teal);
  font-weight: 700;
  flex-shrink: 0;
  margin-top: 1px;
}

/* ---------- Research Areas ---------- */
.research-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 24px;
  margin-top: 48px;
}

.research-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
  display: flex;
  gap: 24px;
  transition: all var(--transition);
}

.research-card:hover {
  border-color: rgba(30, 144, 255, 0.2);
  transform: translateY(-2px);
  box-shadow: var(--shadow-card);
}

.research-card .rc-num {
  font-size: 2.5rem;
  font-weight: 800;
  color: rgba(30, 144, 255, 0.15);
  line-height: 1;
  flex-shrink: 0;
}

.research-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.research-card p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ---------- Products Section ---------- */
.product-showcase {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 48px;
  margin-top: 48px;
  display: flex;
  gap: 48px;
  align-items: center;
}

.product-visual {
  flex: 1;
  min-height: 320px;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, rgba(30, 144, 255, 0.1), rgba(0, 212, 170, 0.05));
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
}

.product-visual .sim-label {
  font-size: 1.8rem;
  font-weight: 800;
  color: rgba(30, 144, 255, 0.2);
  letter-spacing: 4px;
}

.product-info {
  flex: 1;
}

.product-info h3 {
  font-size: 1.8rem;
  font-weight: 700;
  margin-bottom: 16px;
}

.product-info p {
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 24px;
}

.product-features {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 32px;
}

.product-features li {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.product-features li::before {
  content: '✓';
  color: var(--teal);
  font-weight: 700;
}

/* ---------- Journal Section ---------- */
.journal-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 48px;
  margin-top: 48px;
  display: flex;
  gap: 40px;
  align-items: center;
}

.journal-logo-box {
  width: 200px;
  height: 200px;
  border-radius: var(--radius);
  background: linear-gradient(135deg, rgba(30, 144, 255, 0.08), rgba(0, 212, 170, 0.04));
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.journal-logo-box .j-abbr {
  font-size: 2.4rem;
  font-weight: 800;
  color: var(--blue);
  letter-spacing: 3px;
}

.journal-info h3 {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.journal-info p {
  color: var(--text-secondary);
  margin-bottom: 20px;
  line-height: 1.8;
}

.journal-meta {
  display: flex;
  gap: 24px;
  margin-bottom: 24px;
  flex-wrap: wrap;
}

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

/* ---------- Contact Section ---------- */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  margin-top: 48px;
}

.contact-info-list {
  display: flex;
  flex-direction: column;
  gap: 28px;
}

.contact-item {
  display: flex;
  gap: 16px;
  align-items: flex-start;
}

.contact-item .ci-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  background: rgba(30, 144, 255, 0.1);
  color: var(--blue);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  flex-shrink: 0;
}

.contact-item h4 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 4px;
}

.contact-item p {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.contact-form {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.contact-form input,
.contact-form textarea {
  width: 100%;
  padding: 14px 18px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-size: 0.95rem;
  font-family: inherit;
  transition: border-color var(--transition);
}

.contact-form input:focus,
.contact-form textarea:focus {
  outline: none;
  border-color: var(--blue);
}

.contact-form textarea {
  min-height: 120px;
  resize: vertical;
}

.contact-form input::placeholder,
.contact-form textarea::placeholder {
  color: var(--text-muted);
}

/* ---------- Footer ---------- */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  padding: 64px 0 32px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand h3 {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.footer-brand p {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

.footer-col h4 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 2px;
  color: var(--text-muted);
  margin-bottom: 16px;
  font-weight: 600;
}

.footer-col a {
  display: block;
  padding: 4px 0;
  font-size: 0.9rem;
  color: var(--text-secondary);
  transition: color var(--transition);
}

.footer-col a:hover {
  color: var(--text-primary);
}

.footer-bottom {
  border-top: 1px solid var(--border);
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ---------- Scroll Animations ---------- */
.fade-up {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-up.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ---------- Responsive ---------- */
@media (max-width: 1024px) {
  .pillars-grid {
    grid-template-columns: 1fr;
  }

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

  .product-showcase {
    flex-direction: column;
  }

  .journal-card {
    flex-direction: column;
  }

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

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

@media (max-width: 768px) {
  .nav-links {
    display: none;
  }

  .nav-mobile-toggle {
    display: block;
  }

  .nav-links.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: rgba(13, 27, 42, 0.98);
    padding: 16px;
    border-bottom: 1px solid var(--border);
  }

  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .hero h1 {
    font-size: 2rem;
  }

  .hero-tagline {
    font-size: 1rem;
  }

  .section {
    padding: 64px 0;
  }

  .product-features {
    grid-template-columns: 1fr;
  }

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

  .footer-bottom {
    flex-direction: column;
    gap: 12px;
    text-align: center;
  }
}