/* ==========================================
   CSS Custom Properties
   ========================================== */
:root {
  /* Background */
  --bg-primary: #0a0a0f;
  --bg-secondary: #12121a;
  --bg-tertiary: #1a1a28;
  --bg-elevated: #222236;

  /* Accent */
  --accent-start: #6c5ce7;
  --accent-end: #00cec9;
  --accent-gradient: linear-gradient(135deg, var(--accent-start), var(--accent-end));

  /* Text */
  --text-primary: #e8e8f0;
  --text-secondary: #9090a8;
  --text-muted: #606078;

  /* Borders */
  --border-subtle: rgba(255, 255, 255, 0.06);
  --border-focus: var(--accent-start);

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;

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

  /* Shadows */
  --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.4);
  --shadow-glow: 0 0 40px rgba(108, 92, 231, 0.15);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
}

/* ==========================================
   Container
   ========================================== */
.container {
  width: 100%;
  max-width: 800px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

/* ==========================================
   Header
   ========================================== */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(10, 10, 15, 0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-subtle);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  text-decoration: none;
  color: var(--text-primary);
  font-weight: 700;
  font-size: 1.25rem;
}

.logo-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  background: var(--accent-gradient);
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
}

/* ==========================================
   Hero
   ========================================== */
.hero {
  padding: var(--space-2xl) 0;
  text-align: center;
}

.hero-title {
  font-size: clamp(1.75rem, 5vw, 2.5rem);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: var(--space-md);
}

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

.hero-subtitle {
  color: var(--text-secondary);
  font-size: 1.1rem;
}

/* ==========================================
   Converter Card
   ========================================== */
.converter-section {
  padding-bottom: var(--space-2xl);
}

.converter-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  box-shadow: var(--shadow-card);
}

/* ==========================================
   Stages
   ========================================== */
.stage {
  display: none;
}

.stage.active {
  display: block;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ==========================================
   Input
   ========================================== */
.input-group {
  display: flex;
  gap: var(--space-sm);
}

.url-input {
  flex: 1;
  padding: 0.875rem 1rem;
  background: var(--bg-tertiary);
  border: 2px solid var(--border-subtle);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 1rem;
  outline: none;
  transition: border-color var(--transition-fast);
}

.url-input:focus {
  border-color: var(--border-focus);
}

.url-input.error {
  border-color: #e74c3c;
}

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

.input-hint {
  margin-top: var(--space-sm);
  font-size: 0.8rem;
  color: var(--text-muted);
  text-align: center;
}

/* ==========================================
   Buttons
   ========================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 0.875rem 1.5rem;
  border: none;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

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

.btn-primary:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: 0 4px 16px rgba(108, 92, 231, 0.35);
}

.btn-secondary {
  background: var(--bg-elevated);
  color: var(--text-primary);
  border: 1px solid var(--border-subtle);
}

.btn-secondary:hover {
  background: var(--bg-tertiary);
}

.btn-download {
  width: 100%;
  padding: 1rem;
  background: var(--accent-gradient);
  color: white;
  font-size: 1.05rem;
  margin-top: var(--space-lg);
}

.btn-download:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: 0 6px 24px rgba(108, 92, 231, 0.4);
}

.btn-link {
  display: block;
  width: 100%;
  padding: var(--space-md);
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 0.85rem;
  cursor: pointer;
  text-align: center;
  transition: color var(--transition-fast);
}

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

/* ==========================================
   Spinner
   ========================================== */
.spinner {
  width: 20px;
  height: 20px;
  animation: spin 1s linear infinite;
}

.spinner-large {
  width: 50px;
  height: 50px;
  margin: 0 auto var(--space-md);
}

.spinner-large svg {
  width: 100%;
  height: 100%;
  animation: spin 1.2s linear infinite;
}

@keyframes spin {
  100% { transform: rotate(360deg); }
}

.loading-content {
  text-align: center;
  padding: var(--space-xl) 0;
}

.loading-text {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.hidden {
  display: none !important;
}

/* ==========================================
   Video Info
   ========================================== */
.video-info {
  display: flex;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.video-thumbnail {
  width: 160px;
  height: 90px;
  object-fit: cover;
  border-radius: var(--radius-sm);
  background: var(--bg-tertiary);
}

.video-details {
  flex: 1;
  min-width: 0;
}

.video-title {
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.video-duration {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* ==========================================
   Quality Selection
   ========================================== */
.quality-section {
  margin-bottom: var(--space-md);
}

.quality-label {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-sm);
}

.quality-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-sm);
}

.quality-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: var(--space-sm) var(--space-xs);
  background: var(--bg-tertiary);
  border: 2px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.quality-card input {
  display: none;
}

.quality-card:has(input:checked) {
  border-color: var(--accent-start);
  background: var(--bg-elevated);
}

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

.quality-value {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
}

.quality-tag {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
}

/* ==========================================
   Error
   ========================================== */
.error-content {
  text-align: center;
  padding: var(--space-xl) 0;
}

.error-icon {
  width: 48px;
  height: 48px;
  margin: 0 auto var(--space-md);
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(231, 76, 60, 0.15);
  color: #e74c3c;
  border-radius: 50%;
  font-size: 1.5rem;
  font-weight: 700;
}

.error-message {
  color: var(--text-secondary);
  margin-bottom: var(--space-lg);
}

/* ==========================================
   Download Link Container
   ========================================== */
.download-link-container {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  margin-top: var(--space-md);
  padding: var(--space-md);
  background: var(--bg-tertiary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  animation: fadeIn 0.3s ease;
}

.btn-download-direct {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 1rem;
  background: var(--accent-gradient);
  color: white;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 600;
  text-decoration: none;
  transition: all var(--transition-fast);
}

.btn-download-direct:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(108, 92, 231, 0.4);
}

.dl-icon {
  font-size: 1.2rem;
}

.copy-link-btn {
  width: 100%;
  padding: 0.75rem;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  font-size: 0.85rem;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.copy-link-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

/* ==========================================
   Features
   ========================================== */
.features {
  padding: var(--space-2xl) 0;
}

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

.feature-card {
  text-align: center;
  padding: var(--space-lg);
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
}

.feature-icon {
  font-size: 1.5rem;
  margin-bottom: var(--space-sm);
}

.feature-title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: var(--space-xs);
}

.feature-desc {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

/* ==========================================
   FAQ
   ========================================== */
.faq {
  padding: var(--space-2xl) 0;
}

.section-title {
  font-size: 1.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--space-xl);
}

.faq-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.faq-item {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.faq-question {
  padding: var(--space-md);
  cursor: pointer;
  font-weight: 500;
  list-style: none;
}

.faq-question::-webkit-details-marker {
  display: none;
}

.faq-question::after {
  content: '+';
  float: right;
  color: var(--text-muted);
}

.faq-item[open] .faq-question::after {
  content: '−';
}

.faq-answer {
  padding: 0 var(--space-md) var(--space-md);
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.6;
}

/* ==========================================
   Footer
   ========================================== */
.footer {
  margin-top: auto;
  padding: var(--space-xl) 0;
  border-top: 1px solid var(--border-subtle);
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.footer-copy {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.footer-links {
  display: flex;
  gap: var(--space-md);
}

.footer-links a {
  font-size: 0.8rem;
  color: var(--text-muted);
  text-decoration: none;
  transition: color var(--transition-fast);
}

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

/* ==========================================
   Ad Containers
   ========================================== */
.ad-container {
  min-height: 1px;
}

/* ==========================================
   Responsive
   ========================================== */
@media (max-width: 600px) {
  .input-group {
    flex-direction: column;
  }

  .video-info {
    flex-direction: column;
    align-items: center;
    text-align: center;
  }

  .video-thumbnail {
    width: 100%;
    max-width: 320px;
    height: auto;
    aspect-ratio: 16/9;
  }

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

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

  .footer-inner {
    flex-direction: column;
    gap: var(--space-sm);
    text-align: center;
  }
}

@media (max-width: 400px) {
  .alt-links-grid {
    grid-template-columns: 1fr;
  }
}