/* ============================================
   YouTube Danmaku — Design Tokens & Base
   Based on Vercel design system (dark variant)
   Accent: YouTube Red #ff0033
   ============================================ */

:root {
  /* Colors */
  --color-bg: #000000;
  --color-surface: #111111;
  --color-surface-hover: #1a1a1a;
  --color-border: #222222;
  --color-border-hover: #333333;
  --color-text: #ffffff;
  --color-text-muted: #888888;
  --color-text-dim: #555555;
  --color-yt-red: #ff0033;
  --color-yt-red-hover: #cc0029;
  --color-yt-red-dim: rgba(255, 0, 51, 0.15);

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', ui-monospace, monospace;

  /* Spacing (8px base) */
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-5: 48px;
  --space-6: 64px;
  --space-7: 96px;
  --space-8: 128px;

  /* Border Radius */
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;

  /* Container */
  --container-max: 1200px;
  --container-padding: 24px;
}

/* ============================================
   Reset & Base
   ============================================ */

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

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

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
}

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

ul, ol {
  list-style: none;
}

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

/* ============================================
   Typography
   ============================================ */

.text-hero {
  font-size: clamp(40px, 6vw, 72px);
  font-weight: 800;
  line-height: 1.05;
  letter-spacing: -2px;
}

.text-h1 {
  font-size: clamp(32px, 4vw, 48px);
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: -1.5px;
}

.text-h2 {
  font-size: clamp(28px, 3vw, 40px);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -1px;
}

.text-h3 {
  font-size: clamp(20px, 2vw, 24px);
  font-weight: 600;
  line-height: 1.3;
  letter-spacing: -0.5px;
}

.text-body-lg {
  font-size: 18px;
  line-height: 1.6;
}

.text-body {
  font-size: 16px;
  line-height: 1.6;
}

.text-sm {
  font-size: 14px;
  line-height: 1.5;
}

.text-caption {
  font-size: 13px;
  line-height: 1.4;
  color: var(--color-text-muted);
}

.text-mono {
  font-family: var(--font-mono);
}

.text-muted {
  color: var(--color-text-muted);
}

.text-red {
  color: var(--color-yt-red);
}

/* ============================================
   Layout
   ============================================ */

.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
}

.section {
  padding: var(--space-7) 0;
}

.section-sm {
  padding: var(--space-5) 0;
}

/* ============================================
   Header
   ============================================ */

.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: 64px;
  display: flex;
  justify-content: center;
  transition: background-color var(--transition-base), backdrop-filter var(--transition-base);
}

.header.scrolled {
  background-color: rgba(0, 0, 0, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
}

.header-inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  max-width: var(--container-max);
  padding: 0 var(--container-padding);
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  font-weight: 700;
  font-size: 18px;
  letter-spacing: -0.5px;
  flex-shrink: 0;
  min-width: 0;
  margin-right: 40px;
}

.logo-icon {
  width: 32px;
  height: 32px;
}

.logo-text .red {
  color: var(--color-yt-red);
}

.nav {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  flex: 1;
  justify-content: center;
}

.nav-link {
  font-size: 14px;
  font-weight: 500;
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
}

.nav-link:hover {
  color: var(--color-text);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex-shrink: 0;
  margin-left: 40px;
}

/* Hamburger */
.hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 32px;
  height: 32px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.hamburger span {
  display: block;
  width: 100%;
  height: 2px;
  background-color: var(--color-text);
  border-radius: 2px;
  transition: transform var(--transition-fast), opacity var(--transition-fast);
}

.hamburger.active span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

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

.hamburger.active span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Mobile Nav */
.mobile-nav {
  display: none;
  position: fixed;
  top: 64px;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.95);
  backdrop-filter: blur(12px);
  padding: var(--space-4);
  flex-direction: column;
  gap: var(--space-3);
  z-index: 99;
}

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

.mobile-nav .nav-link {
  font-size: 18px;
  padding: var(--space-2) 0;
  border-bottom: 1px solid var(--color-border);
}

/* ============================================
   Buttons
   ============================================ */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 600;
  padding: 10px 20px;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
  text-decoration: none;
}

.btn-primary {
  background-color: var(--color-yt-red);
  color: var(--color-text);
}

.btn-primary:hover {
  background-color: var(--color-yt-red-hover);
  transform: scale(1.02);
}

.btn-secondary {
  background-color: transparent;
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

.btn-secondary:hover {
  border-color: var(--color-border-hover);
  background-color: var(--color-surface);
}

.btn-lg {
  font-size: 16px;
  padding: 14px 28px;
}

.btn:disabled,
.btn.disabled {
  opacity: 0.4;
  cursor: not-allowed;
  pointer-events: none;
}

/* ============================================
   Cards
   ============================================ */

.card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-4);
  transition: border-color var(--transition-fast), transform var(--transition-fast);
}

.card:hover {
  border-color: var(--color-border-hover);
}

.card-interactive:hover {
  transform: translateY(-2px);
  border-color: var(--color-border-hover);
}

.card-sm {
  padding: var(--space-3);
  border-radius: var(--radius-lg);
}

/* ============================================
   Feature Grid
   ============================================ */

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-3);
}

.feature-card {
  padding: var(--space-4);
}

.feature-icon {
  width: 48px;
  height: 48px;
  margin-bottom: var(--space-3);
  color: var(--color-yt-red);
}

.feature-title {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: var(--space-1);
  color: var(--color-text);
}

.feature-desc {
  font-size: 14px;
  line-height: 1.6;
  color: var(--color-text-muted);
}

/* ============================================
   Install Cards
   ============================================ */

.install-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-3);
}

.install-card {
  background-color: #0a0a0a;
  border: 1px solid #1a1a1a;
  border-radius: var(--radius-xl);
  padding: var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.install-card.disabled {
  opacity: 0.5;
}

.install-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.install-card-title {
  font-size: 18px;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.install-card-desc {
  font-size: 14px;
  color: var(--color-text-muted);
  line-height: 1.6;
}

.install-steps {
  margin-top: var(--space-2);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.install-step {
  display: flex;
  gap: var(--space-2);
  align-items: flex-start;
}

.step-num {
  width: 24px;
  height: 24px;
  border-radius: var(--radius-full);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  font-weight: 600;
  flex-shrink: 0;
  color: var(--color-text-muted);
}

.step-text {
  font-size: 14px;
  color: var(--color-text-muted);
  line-height: 1.5;
  padding-top: 2px;
}

/* ============================================
   Tech Stack
   ============================================ */

.tech-grid {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  justify-content: center;
  align-items: center;
}

.tech-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  min-width: 120px;
}

.tech-name {
  font-size: 14px;
  font-weight: 600;
}

.tech-desc {
  font-size: 12px;
  color: var(--color-text-muted);
}

/* ============================================
   Privacy Table
   ============================================ */

.privacy-intro {
  max-width: 700px;
  margin-bottom: var(--space-5);
}

.privacy-promise-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-3);
  margin-bottom: var(--space-5);
}

.promise-item {
  padding: var(--space-3);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  text-align: center;
}

.promise-icon {
  font-size: 24px;
  margin-bottom: var(--space-1);
}

.promise-title {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 4px;
}

.promise-desc {
  font-size: 12px;
  color: var(--color-text-muted);
}

.permissions-table {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.permission-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-2) var(--space-3);
  border-bottom: 1px solid var(--color-border);
  gap: var(--space-3);
}

.permission-row:last-child {
  border-bottom: none;
}

.permission-name {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--color-text);
  background-color: var(--color-surface);
  padding: 4px 10px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--color-border);
  flex-shrink: 0;
}

.permission-desc {
  font-size: 14px;
  color: var(--color-text-muted);
  text-align: right;
}

/* ============================================
   Footer
   ============================================ */

.footer {
  border-top: 1px solid var(--color-border);
  padding: var(--space-5) 0;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}

.footer-links {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.footer-link {
  font-size: 14px;
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
  display: flex;
  align-items: center;
  gap: 6px;
}

.footer-link:hover {
  color: var(--color-text);
}

.footer-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  color: var(--color-text-dim);
  border: 1px solid #333;
  padding: 4px 10px;
  border-radius: var(--radius-full);
}

/* ============================================
   Badges
   ============================================ */

.badge {
  display: inline-flex;
  align-items: center;
  font-size: 11px;
  font-weight: 600;
  padding: 3px 8px;
  border-radius: var(--radius-full);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.badge-soon {
  background-color: #222;
  color: #888;
}

.badge-red {
  background-color: var(--color-yt-red-dim);
  color: var(--color-yt-red);
}

/* ============================================
   Hero Section
   ============================================ */

.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: 64px;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-6);
  align-items: center;
}

.hero-content {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.hero-cta {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.hero-stats {
  display: flex;
  gap: var(--space-3);
  margin-top: var(--space-2);
}

.hero-stat {
  font-size: 13px;
  color: var(--color-text-muted);
  display: flex;
  align-items: center;
  gap: 6px;
}

.hero-stat strong {
  color: var(--color-text);
}

.hero-visual {
  position: relative;
}

/* Hero Video (YouTube embed) */
.hero-video {
  position: relative;
  border-radius: var(--radius-xl);
  overflow: hidden;
  aspect-ratio: 16 / 9;
  background: #000;
  box-shadow: 0 0 0 1px rgba(255,255,255,0.1);
}

.hero-video iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: none;
}

.hero-video .danmaku-demo {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

/* Danmaku Demo */
.danmaku-demo {
  position: absolute;
  inset: 0;
  overflow: hidden;
  pointer-events: none;
}

.danmaku-track {
  position: absolute;
  width: 100%;
  left: 0;
  display: flex;
  align-items: center;
  height: 32px;
}

.danmaku-text {
  position: absolute;
  white-space: nowrap;
  font-size: 14px;
  font-weight: 500;
  color: #fff;
  text-shadow: 0 1px 3px rgba(0,0,0,0.8);
  padding: 4px 10px;
  border-radius: 4px;
  background-color: rgba(0,0,0,0.4);
}

@keyframes danmaku-scroll {
  from { transform: translateX(100vw); }
  to { transform: translateX(-200px); }
}

.dm-1 { top: 8px; animation: danmaku-scroll 8s linear infinite; animation-delay: 0s; color: #ff0033; }
.dm-2 { top: 40px; animation: danmaku-scroll 10s linear infinite; animation-delay: 1.5s; color: #00d4ff; }
.dm-3 { top: 72px; animation: danmaku-scroll 7s linear infinite; animation-delay: 3s; color: #ffcc00; }
.dm-4 { top: 104px; animation: danmaku-scroll 9s linear infinite; animation-delay: 0.5s; color: #00ff88; }
.dm-5 { top: 136px; animation: danmaku-scroll 11s linear infinite; animation-delay: 2s; color: #ff66cc; }
.dm-6 { top: 168px; animation: danmaku-scroll 8s linear infinite; animation-delay: 4s; color: #ff9966; }
.dm-7 { top: 200px; animation: danmaku-scroll 9s linear infinite; animation-delay: 1s; color: #cc99ff; }

/* Play button overlay */
.play-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.play-btn {
  width: 64px;
  height: 64px;
  background-color: rgba(255, 0, 51, 0.9);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: transform var(--transition-fast), background-color var(--transition-fast);
}

.play-btn:hover {
  transform: scale(1.1);
  background-color: var(--color-yt-red);
}

.play-btn svg {
  width: 24px;
  height: 24px;
  fill: white;
  margin-left: 4px;
}

/* ============================================
   Section Headers
   ============================================ */

.section-header {
  text-align: center;
  margin-bottom: var(--space-5);
}

.section-eyebrow {
  font-size: 13px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: var(--color-yt-red);
  margin-bottom: var(--space-1);
}

.section-title {
  margin-bottom: var(--space-2);
}

.section-desc {
  color: var(--color-text-muted);
  font-size: 18px;
  max-width: 600px;
  margin: 0 auto;
}

/* ============================================
   Divider
   ============================================ */

.divider {
  height: 1px;
  background-color: var(--color-border);
  margin: 0;
}

/* ============================================
   Responsive
   ============================================ */

@media (max-width: 1024px) {
  .features-grid {
    grid-template-columns: repeat(2, 1fr);
  }

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

  .hero-grid {
    grid-template-columns: 1fr;
    gap: var(--space-5);
  }

  .hero {
    min-height: auto;
    padding-top: 120px;
    padding-bottom: var(--space-6);
  }

  .hero-visual {
    order: -1;
  }

  .nav {
    gap: var(--space-2);
  }

  .nav-link {
    font-size: 13px;
  }
}

@media (max-width: 640px) {
  :root {
    --container-padding: 16px;
  }

  .features-grid,
  .install-grid,
  .privacy-promise-grid {
    grid-template-columns: 1fr;
  }

  .nav {
    display: none;
  }

  .hamburger {
    display: flex;
  }

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

  .hero-stats {
    flex-direction: column;
    gap: var(--space-1);
  }

  .hero-cta {
    flex-direction: column;
    align-items: flex-start;
  }

  .permission-row {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-1);
  }

  .permission-desc {
    text-align: left;
  }
}