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

:root {
  --primary: #4f46e5;
  --primary-light: #818cf8;
  --primary-dark: #3730a3;
  --bg: #f8fafc;
  --surface: #ffffff;
  --text: #1e293b;
  --text-secondary: #64748b;
  --border: #e2e8f0;
  --border-hover: #cbd5e1;
  --success: #10b981;
  --success-bg: #ecfdf5;
  --danger: #ef4444;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -2px rgba(0,0,0,0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.05);
  --transition: 0.2s ease;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

/* ===== Layout ===== */
.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 20px;
}

/* ===== Header ===== */
.header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(8px);
  background: rgba(255,255,255,0.92);
}

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

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
}

.logo-icon {
  width: 24px;
  height: 24px;
}

.nav {
  display: flex;
  gap: 4px;
  background: var(--bg);
  padding: 4px;
  border-radius: var(--radius-sm);
}

.nav-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  border-radius: 6px;
  transition: all var(--transition);
}

.nav-btn:hover {
  color: var(--text);
  background: rgba(255,255,255,0.6);
}

.nav-btn.active {
  background: var(--surface);
  color: var(--primary);
  box-shadow: var(--shadow);
}

/* ===== Hero ===== */
.hero {
  text-align: center;
  padding: 48px 0 32px;
}

.hero h1 {
  font-size: 2.2rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, var(--primary), var(--primary-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 12px;
}

.hero-sub {
  color: var(--text-secondary);
  font-size: 1.05rem;
  max-width: 520px;
  margin: 0 auto 20px;
}

.badge-row {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px;
}

.badge {
  display: inline-flex;
  align-items: center;
  padding: 4px 12px;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--primary);
  background: rgba(79,70,229,0.08);
  border-radius: 20px;
  letter-spacing: 0.02em;
}

/* ===== Tab Content ===== */
.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

/* ===== Tool Card ===== */
.tool-card {
  background: var(--surface);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  overflow: hidden;
  margin-bottom: 40px;
}

.tool-header {
  padding: 28px 28px 20px;
  border-bottom: 1px solid var(--border);
}

.tool-header h2 {
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 6px;
}

.tool-header p {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* ===== Upload Area ===== */
.upload-area {
  margin: 24px;
  border: 2px dashed var(--border);
  border-radius: var(--radius);
  padding: 48px 24px;
  text-align: center;
  cursor: pointer;
  transition: all var(--transition);
  background: var(--bg);
}

.upload-area:hover,
.upload-area.drag-over {
  border-color: var(--primary-light);
  background: rgba(79,70,229,0.03);
}

.upload-area.drag-over {
  transform: scale(1.01);
}

.upload-icon {
  width: 48px;
  height: 48px;
  color: var(--primary-light);
  margin-bottom: 16px;
}

.upload-text {
  font-size: 1rem;
  color: var(--text);
  margin-bottom: 8px;
}

.upload-link {
  color: var(--primary);
  font-weight: 600;
  text-decoration: underline;
  text-underline-offset: 2px;
}

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

/* ===== Settings ===== */
.settings {
  padding: 24px 28px;
  border-top: 1px solid var(--border);
  background: var(--bg);
}

.settings-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  align-items: end;
}

.setting-item label {
  display: block;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text);
  margin-bottom: 8px;
}

.setting-item label strong {
  color: var(--primary);
}

/* Slider */
.slider {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 6px;
  border-radius: 3px;
  background: var(--border);
  outline: none;
  cursor: pointer;
}

.slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--primary);
  cursor: pointer;
  border: 3px solid var(--surface);
  box-shadow: var(--shadow-md);
  transition: transform var(--transition);
}

.slider::-webkit-slider-thumb:hover {
  transform: scale(1.15);
}

.slider::-moz-range-thumb {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--primary);
  cursor: pointer;
  border: 3px solid var(--surface);
  box-shadow: var(--shadow-md);
}

.slider-labels {
  display: flex;
  justify-content: space-between;
  font-size: 0.7rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

/* Select */
.select-input {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text);
  font-size: 0.875rem;
  cursor: pointer;
  outline: none;
  transition: border-color var(--transition);
}

.select-input:focus {
  border-color: var(--primary-light);
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
  white-space: nowrap;
}

.btn-primary {
  background: var(--primary);
  color: white;
  width: 100%;
}

.btn-primary:hover {
  background: var(--primary-dark);
  box-shadow: var(--shadow-md);
}

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

.btn-success {
  background: var(--success);
  color: white;
  padding: 8px 16px;
  font-size: 0.8rem;
}

.btn-success:hover {
  filter: brightness(0.95);
}

.btn-outline {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border);
  padding: 8px 16px;
  font-size: 0.8rem;
}

.btn-outline:hover {
  border-color: var(--border-hover);
  color: var(--text);
}

/* ===== Results ===== */
.results-area {
  padding: 0 24px 24px;
}

.result-item {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  margin-bottom: 12px;
  transition: border-color var(--transition);
}

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

.result-preview {
  width: 56px;
  height: 56px;
  border-radius: 8px;
  object-fit: cover;
  background: var(--border);
  flex-shrink: 0;
}

.result-audio-icon {
  width: 56px;
  height: 56px;
  border-radius: 8px;
  background: linear-gradient(135deg, var(--primary), var(--primary-light));
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  color: white;
}

.result-info {
  flex: 1;
  min-width: 0;
}

.result-name {
  font-size: 0.9rem;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  margin-bottom: 4px;
}

.result-meta {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8rem;
  color: var(--text-secondary);
}

.size-original {
  text-decoration: line-through;
  opacity: 0.7;
}

.size-arrow {
  color: var(--text-secondary);
}

.size-compressed {
  font-weight: 600;
  color: var(--success);
}

.size-saving {
  display: inline-flex;
  align-items: center;
  padding: 2px 8px;
  background: var(--success-bg);
  color: var(--success);
  border-radius: 12px;
  font-size: 0.7rem;
  font-weight: 700;
}

.result-actions {
  display: flex;
  gap: 8px;
  flex-shrink: 0;
}

/* Progress */
.progress-bar {
  width: 100%;
  height: 4px;
  background: var(--border);
  border-radius: 2px;
  overflow: hidden;
  margin-top: 8px;
}

.progress-fill {
  height: 100%;
  background: var(--primary);
  border-radius: 2px;
  transition: width 0.3s ease;
  width: 0%;
}

.processing-text {
  font-size: 0.75rem;
  color: var(--primary);
  margin-top: 4px;
}

/* ===== Features Section ===== */
.features {
  padding: 60px 0;
  background: var(--surface);
  border-top: 1px solid var(--border);
  margin-top: 20px;
}

.section-title {
  text-align: center;
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 36px;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.feature-card {
  text-align: center;
  padding: 24px 16px;
}

.feature-icon {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(79,70,229,0.08);
  color: var(--primary);
  border-radius: 12px;
  margin: 0 auto 16px;
}

.feature-card h3 {
  font-size: 0.95rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.feature-card p {
  font-size: 0.825rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* ===== Footer ===== */
.footer {
  padding: 32px 0 24px;
  text-align: center;
  border-top: 1px solid var(--border);
  color: var(--text-secondary);
  font-size: 0.8rem;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin-bottom: 12px;
}

.footer-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.85rem;
  transition: color var(--transition);
}

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

/* ===== Static Page Content ===== */
.page-content {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 40px 48px;
  margin: 40px 0;
}

.page-content h1 {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 8px;
  color: var(--text);
}

.page-meta {
  color: var(--text-secondary);
  font-size: 0.85rem;
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}

.page-intro {
  color: var(--text-secondary);
  font-size: 1rem;
  margin-bottom: 32px;
}

.page-content section {
  margin-bottom: 28px;
}

.page-content h2 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text);
}

.page-content h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-top: 16px;
  margin-bottom: 8px;
  color: var(--text);
}

.page-content p {
  color: var(--text-secondary);
  line-height: 1.75;
  margin-bottom: 12px;
}

.page-content ul {
  padding-left: 24px;
  margin-bottom: 12px;
}

.page-content li {
  color: var(--text-secondary);
  line-height: 1.75;
  margin-bottom: 4px;
}

.page-content a {
  color: var(--primary);
  text-decoration: underline;
  text-underline-offset: 2px;
}

.page-content a:hover {
  color: var(--primary-dark);
}

/* About Page Features */
.about-features {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  margin-top: 16px;
}

.about-feature {
  padding: 20px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
}

.about-feature h3 {
  margin-top: 0;
  color: var(--primary);
}

/* Contact Page */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  margin-bottom: 40px;
}

.contact-card {
  padding: 32px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-align: center;
}

.contact-icon {
  width: 56px;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(79,70,229,0.08);
  color: var(--primary);
  border-radius: 14px;
  margin: 0 auto 16px;
}

.contact-card h2 {
  font-size: 1.1rem;
  margin-bottom: 8px;
}

.contact-card p {
  font-size: 0.875rem;
}

.contact-link {
  display: inline-block;
  margin-top: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--primary);
  text-decoration: none;
  word-break: break-all;
}

.contact-link:hover {
  text-decoration: underline;
}

/* FAQ */
.contact-faq {
  margin-top: 40px;
}

.faq-item {
  padding: 20px 0;
  border-bottom: 1px solid var(--border);
}

.faq-item:last-child {
  border-bottom: none;
}

.faq-item h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-top: 0;
  margin-bottom: 8px;
  color: var(--text);
}

.faq-item p {
  margin-bottom: 0;
}

/* ===== Static page responsive ===== */
@media (max-width: 768px) {
  .page-content {
    padding: 28px 24px;
    margin: 24px 0;
  }

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

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

@media (max-width: 480px) {
  .page-content {
    padding: 20px 16px;
    margin: 16px 0;
  }

  .page-content h1 {
    font-size: 1.5rem;
  }

  .footer-links {
    flex-wrap: wrap;
    gap: 12px 20px;
  }
}

/* ===== Download All Bar ===== */
.download-all-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px;
  background: rgba(79,70,229,0.05);
  border: 1px solid rgba(79,70,229,0.15);
  border-radius: var(--radius-sm);
  margin-bottom: 16px;
}

.download-all-bar .summary {
  font-size: 0.85rem;
  color: var(--text);
  font-weight: 500;
}

.download-all-bar .summary strong {
  color: var(--success);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .hero h1 {
    font-size: 1.6rem;
  }

  .hero-sub {
    font-size: 0.9rem;
  }

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

  .features-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
  }

  .result-item {
    flex-wrap: wrap;
  }

  .result-actions {
    width: 100%;
    margin-top: 8px;
  }

  .result-actions .btn {
    flex: 1;
  }

  .download-all-bar {
    flex-direction: column;
    gap: 12px;
    text-align: center;
  }
}

@media (max-width: 480px) {
  .header-inner {
    flex-direction: column;
    height: auto;
    padding: 12px 0;
    gap: 8px;
  }

  .nav {
    width: 100%;
  }

  .nav-btn {
    flex: 1;
    justify-content: center;
  }

  .hero {
    padding: 32px 0 24px;
  }

  .hero h1 {
    font-size: 1.4rem;
  }

  .upload-area {
    margin: 16px;
    padding: 32px 16px;
  }

  .tool-header {
    padding: 20px 16px 16px;
  }

  .settings {
    padding: 20px 16px;
  }

  .results-area {
    padding: 0 16px 16px;
  }

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