/* ===== Design System ===== */
:root {
  /* Colors */
  --bg-primary: #0a0a12;
  --bg-secondary: #12121e;
  --bg-card: rgba(255, 255, 255, 0.04);
  --bg-card-hover: rgba(255, 255, 255, 0.08);
  --text-primary: #f0f0f5;
  --text-secondary: #9898b0;
  --text-muted: #6b6b85;
  --accent-start: #7c5cfc;
  --accent-end: #38b6ff;
  --accent-gradient: linear-gradient(135deg, var(--accent-start), var(--accent-end));
  --accent-glow: rgba(124, 92, 252, 0.25);
  --border-subtle: rgba(255, 255, 255, 0.06);

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  --fs-hero: clamp(2.5rem, 6vw, 4.5rem);
  --fs-h2: clamp(1.75rem, 3.5vw, 2.75rem);
  --fs-h3: clamp(1.15rem, 2vw, 1.5rem);
  --fs-body: 1rem;
  --fs-small: 0.875rem;

  /* Spacing */
  --section-pad: clamp(4rem, 10vh, 8rem) clamp(1.5rem, 5vw, 6rem);
  --card-radius: 1.25rem;
  --btn-radius: 0.75rem;

  /* Transitions */
  --ease-out: cubic-bezier(0.22, 1, 0.36, 1);
  --duration: 0.5s;
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

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

ul {
  list-style: none;
}

/* ===== Utility ===== */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 clamp(1.5rem, 5vw, 3rem);
}

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

.section-title {
  font-size: var(--fs-h2);
  font-weight: 700;
  text-align: center;
  margin-bottom: 1rem;
  letter-spacing: -0.02em;
}

.section-subtitle {
  text-align: center;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 3.5rem;
  font-size: var(--fs-body);
}

/* ===== Animations ===== */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity var(--duration) var(--ease-out),
              transform var(--duration) var(--ease-out);
}

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

.fade-in-delay-1 { transition-delay: 0.1s; }
.fade-in-delay-2 { transition-delay: 0.2s; }
.fade-in-delay-3 { transition-delay: 0.3s; }
.fade-in-delay-4 { transition-delay: 0.4s; }

/* ===== Navigation ===== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  padding: 1rem 0;
  transition: background var(--duration) var(--ease-out),
              box-shadow var(--duration) var(--ease-out);
}

.nav.scrolled {
  background: rgba(10, 10, 18, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  box-shadow: 0 1px 0 var(--border-subtle);
}

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

.nav-logo {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  font-weight: 700;
  font-size: 1.15rem;
}

.nav-logo img {
  width: 36px;
  height: 36px;
  border-radius: 8px;
}

.nav-links {
  display: flex;
  gap: 2rem;
}

.nav-links a {
  color: var(--text-secondary);
  font-size: var(--fs-small);
  font-weight: 500;
  transition: color 0.3s;
  position: relative;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent-gradient);
  border-radius: 1px;
  transition: width 0.3s var(--ease-out);
}

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

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

.nav-mobile-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: 4px;
}

.nav-mobile-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: transform 0.3s, opacity 0.3s;
}

/* ===== Hero ===== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--section-pad);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, var(--accent-glow) 0%, transparent 70%);
  top: 10%;
  left: 50%;
  transform: translateX(-50%);
  pointer-events: none;
  animation: pulse-glow 6s ease-in-out infinite;
}

@keyframes pulse-glow {
  0%, 100% { opacity: 0.5; transform: translateX(-50%) scale(1); }
  50% { opacity: 0.8; transform: translateX(-50%) scale(1.15); }
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 800px;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.4rem 1rem;
  border-radius: 2rem;
  border: 1px solid var(--border-subtle);
  background: var(--bg-card);
  color: var(--text-secondary);
  font-size: var(--fs-small);
  margin-bottom: 2rem;
}

.hero-badge .dot {
  width: 6px;
  height: 6px;
  background: #4ade80;
  border-radius: 50%;
  animation: blink 2s infinite;
}

@keyframes blink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.3; }
}

.hero h1 {
  font-size: var(--fs-hero);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin-bottom: 1.5rem;
}

.hero p {
  font-size: clamp(1rem, 1.8vw, 1.25rem);
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto 2.5rem;
  line-height: 1.8;
}

.hero-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.85rem 2rem;
  background: var(--accent-gradient);
  color: #fff;
  font-weight: 600;
  font-size: var(--fs-body);
  border-radius: var(--btn-radius);
  border: none;
  cursor: pointer;
  transition: transform 0.3s var(--ease-out), box-shadow 0.3s;
}

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

.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.85rem 2rem;
  background: var(--bg-card);
  color: var(--text-primary);
  font-weight: 600;
  font-size: var(--fs-body);
  border-radius: var(--btn-radius);
  border: 1px solid var(--border-subtle);
  cursor: pointer;
  transition: background 0.3s, transform 0.3s var(--ease-out);
}

.btn-secondary:hover {
  background: var(--bg-card-hover);
  transform: translateY(-2px);
}

/* ===== Features ===== */
.features {
  padding: var(--section-pad);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.5rem;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--card-radius);
  padding: 2rem;
  transition: background 0.3s, transform 0.4s var(--ease-out), box-shadow 0.4s;
}

.feature-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
}

.feature-icon {
  width: 52px;
  height: 52px;
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  margin-bottom: 1.25rem;
  background: var(--accent-gradient);
  color: #fff;
}

.feature-card h3 {
  font-size: var(--fs-h3);
  font-weight: 700;
  margin-bottom: 0.65rem;
  letter-spacing: -0.01em;
}

.feature-card p {
  color: var(--text-secondary);
  font-size: var(--fs-small);
  line-height: 1.7;
}

/* ===== Screenshots ===== */
.screenshots {
  padding: var(--section-pad);
  overflow: hidden;
}

.screenshots-wrapper {
  display: flex;
  gap: 2rem;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
}

.screenshot-item {
  flex: 0 1 380px;
  border-radius: var(--card-radius);
  overflow: hidden;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.4);
  transition: transform 0.5s var(--ease-out);
}

.screenshot-item:hover {
  transform: scale(1.03) translateY(-4px);
}

.screenshot-item img {
  width: 100%;
  height: auto;
  display: block;
}

/* ===== About ===== */
.about {
  padding: var(--section-pad);
}

.contact-info {
  display: flex;
  justify-content: center;
}

.contact-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--card-radius);
  padding: 2.5rem 4rem;
  transition: background 0.3s, transform 0.4s var(--ease-out), box-shadow 0.4s;
  text-decoration: none;
  color: inherit;
}

.contact-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
}

.contact-card h3 {
  font-size: var(--fs-h3);
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.contact-card p {
  color: var(--accent-start);
  font-size: var(--fs-body);
}

.about-stats {
  display: flex;
  gap: 3rem;
  justify-content: center;
  margin-top: 2.5rem;
  flex-wrap: wrap;
}

.stat {
  text-align: center;
}

.stat-value {
  font-size: 2rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-label {
  font-size: var(--fs-small);
  color: var(--text-muted);
  margin-top: 0.25rem;
}

/* ===== CTA ===== */
.cta {
  padding: var(--section-pad);
}

.cta-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: calc(var(--card-radius) * 1.5);
  padding: clamp(3rem, 6vw, 5rem);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.cta-box::before {
  content: '';
  position: absolute;
  width: 500px;
  height: 500px;
  background: radial-gradient(circle, var(--accent-glow) 0%, transparent 70%);
  top: -200px;
  right: -100px;
  pointer-events: none;
  opacity: 0.5;
}

.cta-box h2 {
  font-size: var(--fs-h2);
  font-weight: 700;
  margin-bottom: 1rem;
  position: relative;
}

.cta-box p {
  color: var(--text-secondary);
  margin-bottom: 2rem;
  position: relative;
}

.cta-box .btn-primary {
  position: relative;
}

/* ===== Footer ===== */
.footer {
  border-top: 1px solid var(--border-subtle);
  padding: 3rem 0 2rem;
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  flex-wrap: wrap;
  gap: 2rem;
  margin-bottom: 2.5rem;
}

.footer-brand {
  max-width: 300px;
}

.footer-brand .nav-logo {
  margin-bottom: 1rem;
}

.footer-brand p {
  color: var(--text-muted);
  font-size: var(--fs-small);
  line-height: 1.7;
}

.footer-links-group {
  display: flex;
  gap: 4rem;
  flex-wrap: wrap;
}

.footer-column h4 {
  font-size: var(--fs-small);
  font-weight: 600;
  margin-bottom: 1rem;
  color: var(--text-primary);
}

.footer-column a {
  display: block;
  color: var(--text-muted);
  font-size: var(--fs-small);
  margin-bottom: 0.6rem;
  transition: color 0.3s;
}

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

.footer-bottom {
  border-top: 1px solid var(--border-subtle);
  padding-top: 1.5rem;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
  gap: 0;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.footer-bottom span,
.footer-bottom a {
  color: var(--text-muted);
  transition: color 0.3s;
}

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

.footer-sep {
  margin: 0 0.75rem;
  opacity: 0.3;
}

/* ===== Page (Privacy / Terms) ===== */
.page-hero {
  padding: 8rem 0 3rem;
  text-align: center;
}

.page-hero h1 {
  font-size: var(--fs-h2);
  font-weight: 700;
}

.page-hero p {
  color: var(--text-secondary);
  margin-top: 0.5rem;
}

.page-content {
  padding: 0 0 5rem;
}

.page-content .container {
  max-width: 800px;
}

.page-content h2 {
  font-size: var(--fs-h3);
  font-weight: 700;
  margin: 2.5rem 0 1rem;
}

.page-content p,
.page-content li {
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
  line-height: 1.8;
}

.page-content ul {
  padding-left: 1.25rem;
  list-style: disc;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    background: rgba(10, 10, 18, 0.95);
    backdrop-filter: blur(20px);
    padding: 1.5rem;
    gap: 1rem;
    border-bottom: 1px solid var(--border-subtle);
  }

  .nav-links.open {
    display: flex;
  }

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

  .hero {
    min-height: 85vh;
    padding-top: 6rem;
  }

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

  .screenshots-wrapper {
    flex-direction: column;
    align-items: center;
  }

  .screenshot-item {
    flex: 0 1 320px;
  }

  .contact-card {
    padding: 2rem;
  }

  .footer-content {
    flex-direction: column;
  }

  .footer-links-group {
    gap: 2rem;
  }

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

@media (max-width: 480px) {
  .hero-actions {
    flex-direction: column;
    align-items: center;
  }

  .btn-primary,
  .btn-secondary {
    width: 100%;
    justify-content: center;
  }
}