:root {
  --bg: #050814;
  --bg-soft: #0a0f25;
  --glass: rgba(15, 20, 40, 0.35);
  --glass-alt: rgba(20, 25, 50, 0.25);
  --glass-light: rgba(255, 255, 255, 0.05);
  --brand: #4285F4;
  --brand-light: #8AB4F8;
  --brand-dark: #1a73e8;
  --brand-glow: rgba(66, 133, 244, 0.25);
  --accent: #E52592;
  --green: #10b981;
  --red: #ef4444;
  --txt: #f8fafc;
  --txt-mid: #94a3b8;
  --txt-dim: #64748b;
  --bd: rgba(255, 255, 255, 0.15);
  --bd-h: rgba(255, 255, 255, 0.25);
  --font: 'Nunito', 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --mono: 'JetBrains Mono', 'Fira Code', ui-monospace, monospace;
  --r-sm: 10px;
  --r-md: 16px;
  --r-lg: 24px;
  --r-xl: 36px;
  --r-full: 9999px;
  --ease: cubic-bezier(0.2, 0.8, 0.2, 1);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --dur-1: 0.15s;
  --dur-2: 0.25s;
  --dur-3: 0.4s;
  --dur-in: 0.5s;
  --container: 600px;
  --nav-h: 60px;
}

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

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
  font-size: 16px;
  overflow-x: hidden;
}

body {
  font-family: var(--font);
  font-size: 0.9375rem;
  font-weight: 400;
  line-height: 1.6;
  color: var(--txt);
  min-height: 100vh;
  overflow-x: hidden;
  position: relative;
  background-color: #131314;
  background-image: 
      radial-gradient(circle at 15% 50%, rgba(66, 133, 244, 0.15) 0%, transparent 40%),
      radial-gradient(circle at 85% 30%, rgba(155, 81, 224, 0.1) 0%, transparent 40%),
      radial-gradient(circle at 50% 80%, rgba(229, 37, 146, 0.05) 0%, transparent 40%);
  background-size: 200% 200%;
  background-attachment: fixed;
  animation: bg-shift 20s ease-in-out infinite alternate;
  display: flex;
  flex-direction: column;
}

@keyframes bg-shift {
  0% { background-position: 0% 0%; }
  50% { background-position: 100% 100%; }
  100% { background-position: 0% 0%; }
}

@keyframes fadeUp {
  0% { opacity: 0; transform: translateY(20px); }
  100% { opacity: 1; transform: translateY(0); }
}

@keyframes fadeDown {
  0% { opacity: 0; transform: translateY(-20px); }
  100% { opacity: 1; transform: translateY(0); }
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

::selection {
  background: var(--brand-light);
  color: #fff;
}

::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background: rgba(66, 133, 244, 0.3);
  border-radius: var(--r-full);
}

::-webkit-scrollbar-thumb:hover {
  background: rgba(66, 133, 244, 0.5);
}

* {
  scrollbar-width: thin;
  scrollbar-color: rgba(66, 133, 244, 0.3) transparent;
}

a {
  color: var(--brand-light);
  text-decoration: none;
  transition: color var(--dur-1) ease;
}

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

ul, ol {
  list-style: none;
}

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

.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: 1.5rem;
  position: relative;
  z-index: 1;
}

/* Navbar */
.navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  height: var(--nav-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  background: rgba(5, 8, 20, 0.4);
  backdrop-filter: blur(30px) saturate(2);
  -webkit-backdrop-filter: blur(30px) saturate(2);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.nav-container {
  width: 100%;
  max-width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 0.5rem;
}

.navbar-brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-weight: 900;
  font-size: 1.125rem;
  color: var(--txt);
  letter-spacing: -0.02em;
  user-select: none;
  transition: opacity var(--dur-1) ease;
}

.navbar-brand:hover {
  color: var(--txt);
  opacity: 0.9;
}

.navbar-logo {
  width: 28px;
  height: 28px;
  flex-shrink: 0;
  filter: drop-shadow(0 0 10px var(--brand-glow));
}

/* Language Switcher */
.lang-switcher {
  display: flex;
  align-items: center;
  gap: 14px;
}

.lang-btn {
  background: none;
  border: none;
  color: var(--txt-dim);
  font-family: var(--font);
  font-size: 0.85rem;
  font-weight: 800;
  letter-spacing: 0.04em;
  cursor: pointer;
  padding: 4px 2px;
  position: relative;
  transition: color var(--dur-1) ease;
}

.lang-btn:hover {
  color: var(--txt-mid);
}

.lang-btn.active {
  color: var(--txt);
}

.lang-btn.active::after {
  content: '';
  position: absolute;
  left: 0;
  right: 0;
  bottom: -2px;
  height: 2px;
  border-radius: 2px;
  background: var(--brand-light);
  box-shadow: 0 0 8px var(--brand);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  font-family: var(--font);
  font-size: 0.875rem;
  font-weight: 600;
  line-height: 1;
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: var(--r-md);
  cursor: pointer;
  user-select: none;
  white-space: nowrap;
  position: relative;
  overflow: hidden;
  transition: all var(--dur-2) var(--ease);
}

.btn:active {
  transform: scale(0.95);
}

.btn:disabled {
  opacity: 0.5;
  pointer-events: none;
}

.btn .icon {
  flex-shrink: 0;
  width: 18px;
  height: 18px;
}

.btn-primary {
  color: #fff;
  background: #2143a8;
  box-shadow: 0 0 15px rgba(33, 67, 168, 0.2);
  z-index: 1;
}

.btn-primary::before {
  content: '';
  position: absolute;
  inset: 0;
  background: rgba(255, 255, 255, 0.15);
  opacity: 0;
  transition: opacity var(--dur-2) ease;
  z-index: -1;
}

.btn-primary:hover {
  box-shadow: 0 0 15px rgba(255, 255, 255, 0.15);
  color: #fff;
}

.btn-primary:hover::before {
  opacity: 1;
}

.btn-primary:active {
  transform: translateY(0) scale(0.95);
}

/* Hero Section */
.hero {
  padding-top: calc(var(--nav-h) + 4.5rem);
  padding-bottom: 1.5rem;
  text-align: center;
  position: relative;
  z-index: 1;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 18px;
  border-radius: var(--r-full);
  background: rgba(66, 133, 244, 0.15);
  border: 1px solid rgba(66, 133, 244, 0.35);
  color: var(--brand-light);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  margin-bottom: 1.5rem;
  animation: fadeDown var(--dur-in) var(--ease) both;
  box-shadow: 0 0 25px rgba(66, 133, 244, 0.2), inset 0 1px 2px rgba(255, 255, 255, 0.2);
}

.hero-badge svg {
  opacity: 0.9;
}

.hero-title {
  font-size: 3.5rem;
  font-weight: 900;
  line-height: 1.1;
  letter-spacing: -0.04em;
  color: var(--txt);
  margin-bottom: 1rem;
  animation: fadeDown var(--dur-in) var(--ease) 50ms both;
}

.gradient-text {
  background: linear-gradient(90deg, #4285F4, #8AB4F8, #ffffff, #8AB4F8, #4285F4);
  background-size: 300% 100%;
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  animation: gemini-gradient-text 5s linear infinite;
  position: relative;
  display: inline-block;
}

.gradient-text::after {
  content: attr(data-text);
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
  background: inherit;
  background-size: inherit;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  filter: blur(14px);
  opacity: 0.75;
  animation: inherit;
}

@keyframes gemini-gradient-text {
  0% { background-position: 0% 50%; }
  100% { background-position: 300% 50%; }
}

.hero-subtitle {
  font-size: 1.05rem;
  font-weight: 400;
  color: var(--txt-mid);
  max-width: 480px;
  margin-inline: auto;
  line-height: 1.6;
  letter-spacing: -0.01em;
  animation: fadeUp var(--dur-in) var(--ease) 100ms both;
}

/* Main Content Layout */
.page-wrapper {
  display: flex;
  gap: 40px;
  align-items: stretch;
  justify-content: center;
  flex-wrap: wrap;
  width: 100%;
  max-width: 1120px;
  z-index: 1;
  margin: 0 auto;
  padding: 30px 20px 60px;
}

.video-container {
  flex: 1 1 460px;
  max-width: 540px;
  width: 100%;
  text-align: center;
  display: flex;
}

.download-container {
  flex: 1 1 420px;
  max-width: 500px;
  width: 100%;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.glass-card {
  width: 100%;
  background-color: #121520;
  background-image: radial-gradient(circle at top left, rgba(33, 67, 168, 0.15) 0%, transparent 70%);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(196, 199, 197, 0.1);
  box-shadow: 0 0 30px rgba(33, 67, 168, 0.15);
  border-radius: var(--r-xl);
  padding: 2rem;
  transition: all 0.5s cubic-bezier(0.25, 1, 0.5, 1);
  position: relative;
  overflow: hidden;
  animation: fadeUp var(--dur-in) var(--ease) 150ms both;
}

.glass-card:hover {
  transform: translateY(-4px) scale(1.01);
  box-shadow: 0 10px 40px -10px rgba(66, 133, 244, 0.4);
  border-color: rgba(66, 133, 244, 0.4);
}

/* Video Card Header & Toggle */
.tutorial-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.25rem;
}

.tutorial-title {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--txt);
  letter-spacing: -0.01em;
}

.tutor-toggle {
  display: flex;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 10px;
  padding: 3px;
  gap: 4px;
}

.tutor-btn {
  background: transparent;
  border: 1px solid transparent;
  color: var(--txt-dim);
  padding: 5px 10px;
  border-radius: 7px;
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  justify-content: center;
}

.tutor-btn:hover {
  color: var(--txt);
  background: rgba(255, 255, 255, 0.05);
}

.tutor-btn.active {
  color: #fff;
  background: rgba(66, 133, 244, 0.18);
  border-color: rgba(66, 133, 244, 0.45);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.25);
}

.video-frame-wrap {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  border-radius: var(--r-md);
  overflow: hidden;
  background: #05070e;
  border: 1px solid rgba(255, 255, 255, 0.08);
  box-shadow: 0 8px 25px rgba(0, 0, 0, 0.45);
}

.video-frame-wrap iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

/* Download Card */
.dl-card {
  padding: 40px 34px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.dl-title {
  font-size: 2rem;
  font-weight: 900;
  margin-bottom: 28px;
  letter-spacing: -0.02em;
  text-shadow: 0 0 12px rgba(255, 255, 255, 0.35), 0 0 24px rgba(66, 133, 244, 0.25);
}

.dl-btn-wrapper {
  width: 100%;
  max-width: 340px;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.dl-btn {
  padding: 18px 42px;
  font-size: 1.25rem;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  text-decoration: none;
  width: 100%;
  border-radius: var(--r-md);
  background: linear-gradient(135deg, #2b50c7 0%, #2143a8 100%);
  border: 1px solid rgba(138, 180, 248, 0.25);
  box-shadow: 0 6px 24px rgba(33, 67, 168, 0.45), inset 0 1px 1px rgba(255, 255, 255, 0.2);
}

.dl-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 30px rgba(66, 133, 244, 0.5), inset 0 1px 1px rgba(255, 255, 255, 0.3);
}

.dl-btn .chevron {
  width: 18px;
  height: 18px;
  margin-left: 2px;
  transition: transform 0.3s var(--ease);
  opacity: 0.85;
}

.dl-btn.open .chevron {
  transform: rotate(180deg);
}

/* Expandable Download Options Drawer */
.dl-drawer {
  width: 100%;
  max-height: 0;
  opacity: 0;
  overflow: hidden;
  transform: translateY(-8px);
  transition: max-height 0.4s var(--ease), opacity 0.3s var(--ease), transform 0.35s var(--ease), margin-top 0.3s var(--ease);
  margin-top: 0;
}

.dl-drawer.open {
  max-height: 280px;
  opacity: 1;
  transform: translateY(0);
  margin-top: 14px;
}

.dl-options {
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 4px 2px;
}

.dl-option-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  padding: 14px 18px;
  border-radius: var(--r-md);
  background: rgba(8, 12, 26, 0.75);
  border: 1px solid rgba(255, 255, 255, 0.12);
  text-align: left;
  color: var(--txt);
  text-decoration: none;
  transition: all 0.22s var(--ease);
  position: relative;
  overflow: hidden;
}

.dl-option-item:hover {
  color: var(--txt);
  background: rgba(33, 67, 168, 0.28);
  border-color: rgba(66, 133, 244, 0.55);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.35), 0 0 18px rgba(66, 133, 244, 0.2);
}

.dl-option-item:active {
  transform: scale(0.98);
}

.dl-option-info {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.dl-option-title {
  font-size: 0.98rem;
  font-weight: 800;
  color: var(--txt);
  display: flex;
  align-items: center;
  gap: 8px;
}

.dl-option-badge {
  font-size: 0.65rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 2px 7px;
  border-radius: var(--r-full);
  background: rgba(66, 133, 244, 0.2);
  border: 1px solid rgba(66, 133, 244, 0.4);
  color: var(--brand-light);
}

.dl-option-badge.delta {
  background: rgba(229, 37, 146, 0.18);
  border-color: rgba(229, 37, 146, 0.4);
  color: #f472b6;
}

.dl-option-sub {
  font-size: 0.8rem;
  color: var(--txt-mid);
  font-weight: 500;
}

.dl-option-icon {
  width: 34px;
  height: 34px;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.08);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  color: var(--brand-light);
  transition: all 0.2s ease;
}

.dl-option-item:hover .dl-option-icon {
  background: var(--brand);
  border-color: var(--brand-light);
  color: #fff;
}

.dl-note {
  font-size: 0.82rem;
  color: var(--txt-dim);
  margin-top: 22px;
  max-width: 340px;
  line-height: 1.5;
}

/* VirusTotal Button */
.vt-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  background: rgba(66, 133, 244, 0.1);
  border: 1px solid rgba(66, 133, 244, 0.4);
  border-radius: 12px;
  color: var(--txt);
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
  margin-top: 24px;
}

.vt-btn:hover {
  background: rgba(66, 133, 244, 0.25);
  border-color: #4285F4;
  color: var(--txt);
  box-shadow: 0 6px 20px rgba(66, 133, 244, 0.4);
  transform: translateY(-2px);
}

.vt-btn svg {
  width: 18px;
  height: 18px;
  stroke: var(--brand-light);
}

@media (max-width: 768px) {
  .page-wrapper {
    flex-direction: column-reverse;
    gap: 20px;
    padding: 10px 20px 40px;
  }
  .hero {
    padding-top: calc(var(--nav-h) + 1.5rem) !important;
    padding-bottom: 0 !important;
  }
  .hero-title {
    font-size: 2.2rem !important;
    margin-bottom: 0.5rem !important;
  }
  .hero-subtitle {
    font-size: 1rem !important;
    margin-bottom: 1.5rem !important;
  }
  .dl-card {
    padding: 24px 20px !important;
  }
  .dl-title {
    font-size: 1.5rem !important;
    margin-bottom: 18px !important;
  }
  .dl-btn {
    padding: 15px 20px;
    font-size: 1.15rem;
    width: 100%;
    justify-content: center;
  }
  .vt-btn {
    margin-top: 16px;
  }
}