/* ============================================
   CloudSync - Enterprise Collaboration Platform
   Mobile-First Responsive Stylesheet
   ============================================ */

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

:root {
  --color-primary: #1a56db;
  --color-primary-dark: #1340a8;
  --color-primary-light: #e8effc;
  --color-secondary: #0f9d8f;
  --color-accent: #f59e0b;
  --color-bg: #ffffff;
  --color-bg-alt: #f8fafc;
  --color-bg-dark: #0f172a;
  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-text-light: #94a3b8;
  --color-border: #e2e8f0;
  --color-white: #ffffff;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -2px rgba(0,0,0,0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.04);
  --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.08), 0 8px 10px -6px rgba(0,0,0,0.04);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --max-width: 1200px;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

ul, ol {
  list-style: none;
}

button {
  border: none;
  background: none;
  cursor: pointer;
  font-family: inherit;
  font-size: inherit;
}

/* Utility */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

.section {
  padding: 60px 0;
}

.section-title {
  font-size: 26px;
  font-weight: 700;
  color: var(--color-text);
  text-align: center;
  margin-bottom: 12px;
  line-height: 1.3;
}

.section-subtitle {
  font-size: 15px;
  color: var(--color-text-secondary);
  text-align: center;
  max-width: 600px;
  margin: 0 auto 40px;
  line-height: 1.6;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 12px 28px;
  border-radius: var(--radius-sm);
  font-size: 15px;
  font-weight: 600;
  transition: var(--transition);
  white-space: nowrap;
}

.btn-primary {
  background: var(--color-primary);
  color: var(--color-white);
  box-shadow: 0 2px 8px rgba(26, 86, 219, 0.3);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  box-shadow: 0 4px 12px rgba(26, 86, 219, 0.4);
  transform: translateY(-1px);
}

.btn-outline {
  border: 1.5px solid var(--color-primary);
  color: var(--color-primary);
  background: transparent;
}

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

/* ========================
   Navigation
   ======================== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  transition: var(--transition);
}

.navbar.scrolled {
  box-shadow: var(--shadow-md);
}

.navbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.navbar-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 700;
  color: var(--color-primary);
}

.navbar-brand svg {
  width: 32px;
  height: 32px;
}

.navbar-links {
  display: none;
  gap: 32px;
}

.navbar-links a {
  font-size: 15px;
  font-weight: 500;
  color: var(--color-text-secondary);
  position: relative;
  padding: 4px 0;
}

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

.navbar-links a::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--color-primary);
  transition: var(--transition);
}

.navbar-links a:hover::after,
.navbar-links a.active::after {
  width: 100%;
}

.navbar-cta {
  display: none;
}

/* Language Switcher */
.lang-switcher {
  position: relative;
  display: flex;
  align-items: center;
}

.lang-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
  background: transparent;
  border: none;
  padding: 0;
}

.lang-btn:hover {
  background: var(--color-bg-alt);
}

.lang-btn svg {
  width: 20px;
  height: 20px;
  color: var(--color-text-secondary);
}

.lang-dropdown {
  display: none;
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 140px;
  background: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  z-index: 1001;
  overflow: hidden;
}

.lang-dropdown.active {
  display: block;
}

.lang-option {
  display: flex;
  align-items: center;
  gap: 10px;
  width: 100%;
  min-height: 44px;
  padding: 10px 16px;
  font-size: 14px;
  color: var(--color-text);
  cursor: pointer;
  transition: var(--transition);
  border: none;
  background: none;
  text-align: left;
}

.lang-option:hover {
  background: var(--color-bg-alt);
}

.lang-option.active {
  color: var(--color-primary);
  font-weight: 600;
  background: var(--color-primary-light);
}

.lang-flag {
  font-size: 16px;
  line-height: 1;
}

.hamburger {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 44px;
  height: 44px;
  cursor: pointer;
  gap: 5px;
}

.hamburger span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: var(--transition);
}

.hamburger.active span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.hamburger.active span:nth-child(2) {
  opacity: 0;
}

.hamburger.active span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* Mobile Menu */
.mobile-menu {
  display: none;
  position: fixed;
  top: 64px;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--color-bg);
  z-index: 999;
  padding: 20px;
  flex-direction: column;
  gap: 0;
  overflow-y: auto;
}

.mobile-menu.active {
  display: flex;
}

.mobile-menu a {
  display: flex;
  align-items: center;
  min-height: 52px;
  padding: 14px 16px;
  font-size: 16px;
  font-weight: 500;
  color: var(--color-text);
  border-bottom: 1px solid var(--color-border);
}

.mobile-menu a:hover {
  color: var(--color-primary);
  background: var(--color-primary-light);
  border-radius: var(--radius-sm);
}

.mobile-menu .mobile-cta {
  margin-top: 20px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

/* ========================
   Hero Section
   ======================== */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: 80px;
  padding-bottom: 40px;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 0;
}

.hero-bg img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.hero-bg::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(135deg, rgba(15, 23, 42, 0.82) 0%, rgba(26, 86, 219, 0.65) 100%);
}

.hero-content {
  position: relative;
  z-index: 1;
  text-align: center;
  color: var(--color-white);
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 16px;
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.25);
  border-radius: 50px;
  font-size: 13px;
  font-weight: 500;
  margin-bottom: 24px;
  backdrop-filter: blur(4px);
}

.hero-badge-dot {
  width: 6px;
  height: 6px;
  background: #34d399;
  border-radius: 50%;
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.hero h1 {
  font-size: 30px;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 16px;
  letter-spacing: -0.02em;
}

.hero-desc {
  font-size: 15px;
  line-height: 1.7;
  color: rgba(255, 255, 255, 0.85);
  max-width: 560px;
  margin: 0 auto 32px;
}

.hero-buttons {
  display: flex;
  flex-direction: column;
  gap: 12px;
  align-items: center;
}

.hero-buttons .btn {
  width: 100%;
  max-width: 280px;
}

.hero-buttons .btn-white {
  background: var(--color-white);
  color: var(--color-primary);
  font-weight: 600;
}

.hero-buttons .btn-white:hover {
  background: #f1f5f9;
  transform: translateY(-1px);
}

.hero-buttons .btn-ghost {
  border: 1.5px solid rgba(255, 255, 255, 0.5);
  color: var(--color-white);
}

.hero-buttons .btn-ghost:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: rgba(255, 255, 255, 0.8);
}

.hero-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin-top: 48px;
  padding-top: 32px;
  border-top: 1px solid rgba(255, 255, 255, 0.15);
}

.hero-stat-number {
  font-size: 24px;
  font-weight: 800;
  color: var(--color-white);
}

.hero-stat-label {
  font-size: 12px;
  color: rgba(255, 255, 255, 0.7);
  margin-top: 4px;
}

/* ========================
   Features Section
   ======================== */
.features {
  background: var(--color-bg-alt);
}

.features-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
}

.feature-card {
  background: var(--color-white);
  border-radius: var(--radius-lg);
  padding: 28px 24px;
  border: 1px solid var(--color-border);
  transition: var(--transition);
}

.feature-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
  border-color: transparent;
}

.feature-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 16px;
}

.feature-icon svg {
  width: 24px;
  height: 24px;
}

.feature-icon.blue { background: #dbeafe; color: #1d4ed8; }
.feature-icon.green { background: #d1fae5; color: #059669; }
.feature-icon.purple { background: #ede9fe; color: #7c3aed; }
.feature-icon.orange { background: #ffedd5; color: #ea580c; }

.feature-card h3 {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--color-text);
}

.feature-card p {
  font-size: 14px;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* ========================
   About Section
   ======================== */
.about-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 32px;
  align-items: center;
}

.about-image {
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.about-image img {
  width: 100%;
  height: auto;
  display: block;
}

.about-content h2 {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 16px;
  line-height: 1.3;
}

.about-content p {
  font-size: 15px;
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin-bottom: 16px;
}

.about-list {
  margin-top: 20px;
}

.about-list-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  margin-bottom: 14px;
}

.about-list-icon {
  flex-shrink: 0;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--color-primary-light);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-top: 2px;
}

.about-list-icon svg {
  width: 12px;
  height: 12px;
  color: var(--color-primary);
}

.about-list-item span {
  font-size: 15px;
  color: var(--color-text);
  line-height: 1.5;
}

/* ========================
   Clients / Trust Section
   ======================== */
.clients {
  background: var(--color-bg-alt);
}

.clients-logos {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin-bottom: 40px;
}

.client-logo {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px 16px;
  background: var(--color-white);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  font-size: 14px;
  font-weight: 600;
  color: var(--color-text-secondary);
  text-align: center;
  min-height: 72px;
}

.stats-row {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
}

.stat-card {
  text-align: center;
  padding: 24px 16px;
  background: var(--color-white);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
}

.stat-number {
  font-size: 28px;
  font-weight: 800;
  color: var(--color-primary);
  margin-bottom: 4px;
}

.stat-label {
  font-size: 13px;
  color: var(--color-text-secondary);
}

/* ========================
   FAQ Section
   ======================== */
.faq-list {
  max-width: 720px;
  margin: 0 auto;
}

.faq-item {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  margin-bottom: 12px;
  overflow: hidden;
  transition: var(--transition);
}

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

.faq-question {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  min-height: 52px;
  padding: 16px 20px;
  text-align: left;
  font-size: 15px;
  font-weight: 600;
  color: var(--color-text);
  cursor: pointer;
  background: var(--color-white);
  gap: 12px;
}

.faq-question svg {
  flex-shrink: 0;
  width: 20px;
  height: 20px;
  color: var(--color-text-light);
  transition: var(--transition);
}

.faq-item.active .faq-question svg {
  transform: rotate(180deg);
  color: var(--color-primary);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
}

.faq-answer-inner {
  padding: 0 20px 16px;
  font-size: 14px;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

.faq-item.active .faq-answer {
  max-height: 300px;
}

/* ========================
   Contact Section
   ======================== */
.contact {
  background: var(--color-bg-alt);
}

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

.contact-info h3 {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 16px;
}

.contact-info p {
  font-size: 14px;
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin-bottom: 20px;
}

.contact-detail {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 14px;
}

.contact-detail-icon {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  background: var(--color-primary-light);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.contact-detail-icon svg {
  width: 18px;
  height: 18px;
  color: var(--color-primary);
}

.contact-detail span {
  font-size: 14px;
  color: var(--color-text);
}

.contact-form {
  background: var(--color-white);
  padding: 24px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
}

.form-group {
  margin-bottom: 16px;
}

.form-group label {
  display: block;
  font-size: 14px;
  font-weight: 500;
  color: var(--color-text);
  margin-bottom: 6px;
}

.form-group input,
.form-group textarea,
.form-group select {
  width: 100%;
  min-height: 44px;
  padding: 10px 14px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: 15px;
  font-family: inherit;
  color: var(--color-text);
  background: var(--color-bg);
  transition: var(--transition);
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(26, 86, 219, 0.1);
}

.form-group textarea {
  min-height: 100px;
  resize: vertical;
}

.form-submit {
  width: 100%;
  min-height: 48px;
}

/* ========================
   Footer
   ======================== */
.footer {
  background: var(--color-bg-dark);
  color: rgba(255, 255, 255, 0.8);
  padding: 48px 0 24px;
}

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

.footer-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 700;
  color: var(--color-white);
  margin-bottom: 12px;
}

.footer-brand svg {
  width: 28px;
  height: 28px;
}

.footer-desc {
  font-size: 14px;
  color: rgba(255, 255, 255, 0.6);
  line-height: 1.6;
  max-width: 300px;
}

.footer-col h4 {
  font-size: 15px;
  font-weight: 600;
  color: var(--color-white);
  margin-bottom: 16px;
}

.footer-col a {
  display: block;
  font-size: 14px;
  color: rgba(255, 255, 255, 0.6);
  padding: 5px 0;
  min-height: 36px;
  display: flex;
  align-items: center;
}

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

.footer-bottom {
  padding-top: 24px;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  display: flex;
  flex-direction: column;
  gap: 12px;
  align-items: center;
  text-align: center;
}

.footer-copyright {
  font-size: 13px;
  color: rgba(255, 255, 255, 0.5);
}

.footer-links {
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
  justify-content: center;
}

.footer-links a {
  font-size: 13px;
  color: rgba(255, 255, 255, 0.5);
}

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

/* ========================
   Privacy / Terms Page
   ======================== */
.legal-page {
  display: none;
  padding-top: 80px;
  min-height: 100vh;
}

.legal-page.active {
  display: block;
}

.legal-content {
  max-width: 720px;
  margin: 0 auto;
  padding: 40px 20px;
}

.legal-content h1 {
  font-size: 26px;
  font-weight: 700;
  margin-bottom: 24px;
}

.legal-content h2 {
  font-size: 18px;
  font-weight: 600;
  margin: 24px 0 12px;
}

.legal-content p {
  font-size: 15px;
  color: var(--color-text-secondary);
  line-height: 1.8;
  margin-bottom: 12px;
}

.legal-back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  color: var(--color-primary);
  margin-bottom: 24px;
  min-height: 44px;
}

/* ========================
   Animations
   ======================== */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* ========================
   Tablet (>=640px)
   ======================== */
@media (min-width: 640px) {
  .container {
    padding: 0 32px;
  }

  .section {
    padding: 80px 0;
  }

  .section-title {
    font-size: 32px;
  }

  .section-subtitle {
    font-size: 16px;
  }

  .hero h1 {
    font-size: 38px;
  }

  .hero-desc {
    font-size: 16px;
  }

  .hero-buttons {
    flex-direction: row;
    justify-content: center;
  }

  .hero-buttons .btn {
    width: auto;
  }

  .hero-stat-number {
    font-size: 30px;
  }

  .features-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
  }

  .clients-logos {
    grid-template-columns: repeat(4, 1fr);
  }

  .stats-row {
    grid-template-columns: repeat(4, 1fr);
  }

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

  .footer-grid {
    grid-template-columns: 2fr 1fr 1fr;
  }

  .footer-bottom {
    flex-direction: row;
    justify-content: space-between;
  }
}

/* ========================
   Desktop (>=1024px)
   ======================== */
@media (min-width: 1024px) {
  .container {
    padding: 0 40px;
  }

  .section {
    padding: 100px 0;
  }

  .section-title {
    font-size: 36px;
  }

  .navbar-links {
    display: flex;
  }

  .navbar-cta {
    display: flex;
    align-items: center;
    gap: 12px;
  }

  .hamburger {
    display: none;
  }

  .hero {
    min-height: 90vh;
  }

  .hero h1 {
    font-size: 48px;
  }

  .hero-desc {
    font-size: 17px;
  }

  .hero-stat-number {
    font-size: 36px;
  }

  .hero-stat-label {
    font-size: 14px;
  }

  .features-grid {
    grid-template-columns: repeat(4, 1fr);
  }

  .about-grid {
    grid-template-columns: 1fr 1fr;
    gap: 60px;
  }

  .about-content h2 {
    font-size: 32px;
  }

  .footer-grid {
    grid-template-columns: 2fr 1fr 1fr 1fr;
  }
}