:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f5f5f7;
  --bg-dark: #000000;
  --text-primary: #1d1d1f;
  --text-secondary: #6e6e73;
  --accent: #0071e3;
  --accent-hover: #0077ed;
  --border: rgba(0,0,0,0.08);
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  --radius: 18px;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Display", "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

/* Navigation */
.navbar {
  position: sticky;
  top: 0;
  background: rgba(255,255,255,0.8);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
  padding: 16px 0;
}

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

.nav-brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #000, #333);
  border-radius: 12px;
  font-weight: 700;
  font-size: 16px;
  color: white;
}

.logo-img {
  width: 44px;
  height: 44px;
  border-radius: 12px;
  object-fit: cover;
}

.logo-small {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #000, #333);
  border-radius: 10px;
  font-weight: 700;
  font-size: 14px;
  color: white;
}

.logo-img-small {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  object-fit: cover;
}

.brand-name {
  font-size: 22px;
  font-weight: 600;
  color: var(--text-primary);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-primary);
  font-size: 14px;
  font-weight: 500;
  transition: var(--transition);
}

.nav-links a:hover {
  color: var(--accent);
}

.btn-nav {
  padding: 8px 16px;
  border-radius: 24px;
  font-weight: 600;
  background: var(--accent);
  color: white !important;
  transition: var(--transition);
}

.btn-nav:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
  color: white !important;
}

.btn-nav.ghost {
  background: transparent;
  color: var(--text-primary) !important;
  border: 1px solid var(--border);
}

.btn-nav.ghost:hover {
  background: var(--bg-secondary);
  color: var(--text-primary) !important;
}

/* Hero Section */
.hero {
  background: linear-gradient(180deg, #ffffff 0%, #f5f5f7 100%);
  padding: 120px 0;
  text-align: center;
}

.hero-content {
  max-width: 900px;
}

.hero-title {
  font-size: 72px;
  font-weight: 700;
  line-height: 1.1;
  margin-bottom: 24px;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, #000 0%, #333 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 24px;
  color: var(--text-secondary);
  margin-bottom: 40px;
  line-height: 1.5;
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}

.hero-cta {
  display: flex;
  gap: 16px;
  justify-content: center;
  margin-bottom: 24px;
}

.btn-hero {
  padding: 16px 32px;
  border-radius: 32px;
  font-size: 17px;
  font-weight: 600;
  text-decoration: none;
  transition: var(--transition);
  display: inline-block;
}

.btn-hero.primary {
  background: var(--accent);
  color: white;
}

.btn-hero.primary:hover {
  background: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-hero.secondary {
  background: transparent;
  color: var(--accent);
  border: 2px solid var(--accent);
}

.btn-hero.secondary:hover {
  background: var(--accent);
  color: white;
}

.hero-note {
  color: var(--text-secondary);
  font-size: 14px;
}

/* GitHub Banner */
.github-banner {
  background: linear-gradient(135deg, #000 0%, #1a1a1a 100%);
  color: white;
  padding: 48px 0;
}

.banner-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 32px;
}

.banner-text h2 {
  font-size: 32px;
  margin-bottom: 12px;
  font-weight: 700;
}

.banner-text p {
  color: rgba(255,255,255,0.8);
  font-size: 17px;
}

.btn-banner {
  padding: 16px 32px;
  background: white;
  color: #000;
  border-radius: 32px;
  text-decoration: none;
  font-weight: 600;
  font-size: 17px;
  white-space: nowrap;
  transition: var(--transition);
}

.btn-banner:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(255,255,255,0.3);
}

/* Features Section */
.features-section {
  padding: 100px 0;
  background: var(--bg-primary);
}

.section-title {
  font-size: 48px;
  font-weight: 700;
  text-align: center;
  margin-bottom: 16px;
  letter-spacing: -0.01em;
}

.section-subtitle {
  font-size: 21px;
  color: var(--text-secondary);
  text-align: center;
  margin-bottom: 64px;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 32px;
}

.feature-card {
  background: var(--bg-primary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px 32px;
  transition: var(--transition);
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: rgba(0,0,0,0.12);
}

.feature-icon {
  font-size: 48px;
  margin-bottom: 20px;
  color: var(--accent);
}

.feature-icon i {
  width: 48px;
  height: 48px;
  stroke-width: 1.5;
}

.feature-card h3 {
  font-size: 24px;
  margin-bottom: 12px;
  font-weight: 600;
}

.feature-card p {
  color: var(--text-secondary);
  font-size: 16px;
  line-height: 1.6;
}

/* How it Works */
.how-section {
  padding: 100px 0;
  background: var(--bg-secondary);
}

.steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 48px;
  margin-top: 64px;
}

.step {
  text-align: center;
}

.step-number {
  width: 64px;
  height: 64px;
  background: var(--bg-dark);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 28px;
  font-weight: 700;
  margin: 0 auto 24px;
}

.step h3 {
  font-size: 24px;
  margin-bottom: 12px;
  font-weight: 600;
}

.step p {
  color: var(--text-secondary);
  font-size: 16px;
  line-height: 1.6;
}

/* FAQ Section */
.faq-section {
  padding: 100px 0;
  background: var(--bg-primary);
}

.faq-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(450px, 1fr));
  gap: 40px;
  margin-top: 64px;
}

.faq-item h3 {
  font-size: 21px;
  margin-bottom: 12px;
  font-weight: 600;
}

.faq-item p {
  color: var(--text-secondary);
  font-size: 16px;
  line-height: 1.7;
}

/* Download CTA */
.download-cta {
  background: linear-gradient(135deg, var(--accent) 0%, #005bb5 100%);
  color: white;
  padding: 80px 0;
  text-align: center;
}

.cta-content h2 {
  font-size: 42px;
  margin-bottom: 16px;
  font-weight: 700;
}

.cta-content p {
  font-size: 21px;
  margin-bottom: 32px;
  opacity: 0.95;
}

.btn-cta {
  padding: 18px 40px;
  background: white;
  color: var(--accent);
  border-radius: 32px;
  text-decoration: none;
  font-weight: 600;
  font-size: 18px;
  display: inline-block;
  transition: var(--transition);
}

.btn-cta:hover {
  transform: translateY(-2px);
  box-shadow: 0 12px 32px rgba(0,0,0,0.2);
}

/* Footer */
.footer {
  background: var(--bg-dark);
  color: white;
  padding: 64px 0 32px;
}

.footer-content {
  display: flex;
  justify-content: space-between;
  gap: 64px;
  margin-bottom: 48px;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
  font-size: 20px;
  font-weight: 600;
}

.footer-left p {
  color: rgba(255,255,255,0.6);
  font-size: 14px;
}

.footer-links {
  display: flex;
  gap: 80px;
}

.footer-col h4 {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 16px;
  opacity: 0.6;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.footer-col a {
  display: block;
  color: rgba(255,255,255,0.8);
  text-decoration: none;
  margin-bottom: 12px;
  font-size: 15px;
  transition: var(--transition);
}

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

.footer-bottom {
  padding-top: 32px;
  border-top: 1px solid rgba(255,255,255,0.1);
  text-align: center;
}

.footer-bottom p {
  color: rgba(255,255,255,0.5);
  font-size: 14px;
}

/* Responsive */
@media (max-width: 768px) {
  .nav-links {
    gap: 16px;
  }
  
  .nav-links a:not(.btn-nav) {
    display: none;
  }
  
  .hero-title {
    font-size: 48px;
  }
  
  .hero-subtitle {
    font-size: 18px;
  }
  
  .hero-cta {
    flex-direction: column;
  }
  
  .btn-hero {
    width: 100%;
    text-align: center;
  }
  
  .banner-content {
    flex-direction: column;
    text-align: center;
  }
  
  .btn-banner {
    width: 100%;
  }
  
  .features-grid,
  .faq-grid {
    grid-template-columns: 1fr;
  }
  
  .footer-content {
    flex-direction: column;
    gap: 32px;
  }
  
  .footer-links {
    gap: 40px;
  }
  
  .section-title {
    font-size: 36px;
  }
}

@media (max-width: 480px) {
  .hero {
    padding: 80px 0;
  }
  
  .hero-title {
    font-size: 36px;
  }
  
  .features-section,
  .how-section,
  .faq-section {
    padding: 60px 0;
  }
}

/* Screen-reader-only (visible to assistive tech, hidden visually) */
.sr-only {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  padding: 0 !important;
  margin: -1px !important;
  overflow: hidden !important;
  clip: rect(0, 0, 0, 0) !important;
  white-space: nowrap !important;
  border: 0 !important;
}