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

:root {
  --primary-color: #3b82f6;
  --primary-hover: #2563eb;
  --secondary-color: #64748b;
  --background: #f8fafc;
  --card-bg: #ffffff;
  --text: #1e293b;
  --text-secondary: #64748b;
  --border: #e2e8f0;
  --success: #10b981;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  background: var(--background);
  color: var(--text);
  line-height: 1.6;
}

header {
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

nav {
  max-width: 1400px;
  margin: 0 auto;
  padding: 1rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-brand a {
  font-size: 1.5rem;
  font-weight: bold;
  color: var(--primary-color);
  text-decoration: none;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 2rem;
}

.nav-links a {
  color: var(--text);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.2s;
}

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

.nav-tools select {
  padding: 0.5rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--card-bg);
}

.ad-banner {
  width: 100%;
  background: #e2e8f0;
  padding: 1rem;
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.ad-banner.top {
  border-bottom: 1px solid var(--border);
}

.ad-banner.bottom {
  border-top: 1px solid var(--border);
}

.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 2rem;
}

.hero {
  text-align: center;
  margin-bottom: 3rem;
}

.hero h1 {
  font-size: 2.5rem;
  margin-bottom: 0.5rem;
  color: var(--text);
}

.hero p {
  font-size: 1.125rem;
  color: var(--text-secondary);
}

.main-content {
  display: grid;
  grid-template-columns: 160px 1fr 160px;
  gap: 2rem;
}

.sidebar {
  display: flex;
  flex-direction: column;
}

.ad-sidebar {
  background: #e2e8f0;
  padding: 2rem 1rem;
  text-align: center;
  color: var(--text-secondary);
  border-radius: 8px;
  min-height: 400px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.converter {
  background: var(--card-bg);
  border-radius: 12px;
  padding: 2rem;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.upload-area {
  border: 2px dashed var(--border);
  border-radius: 12px;
  padding: 3rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s;
  background: var(--background);
}

.upload-area:hover,
.upload-area.dragover {
  border-color: var(--primary-color);
  background: #eff6ff;
}

.dropzone-content svg {
  width: 64px;
  height: 64px;
  margin-bottom: 1rem;
  color: var(--primary-color);
}

.dropzone-content p {
  margin: 0.5rem 0;
}

.dropzone-content .subtext {
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.presets {
  display: flex;
  gap: 1rem;
  margin: 2rem 0;
  flex-wrap: wrap;
  justify-content: center;
}

.preset {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  border: 2px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s;
  background: var(--card-bg);
}

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

.preset input:checked + span {
  font-weight: 600;
  color: var(--primary-color);
}

.preset:has(input:checked) {
  border-color: var(--primary-color);
  background: #eff6ff;
}

.preset input {
  width: 18px;
  height: 18px;
  accent-color: var(--primary-color);
}

.actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  margin: 2rem 0;
}

.btn {
  padding: 0.75rem 2rem;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}

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

.btn.primary:hover {
  background: var(--primary-hover);
}

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

.btn.secondary:hover {
  background: #475569;
}

.btn.small {
  padding: 0.5rem 1rem;
  font-size: 0.875rem;
}

.btn.remove-btn {
  padding: 0.25rem 0.75rem;
  background: #ef4444;
  color: white;
}

.btn.download-btn {
  background: var(--success);
  color: white;
}

.btn.download-btn:hover {
  background: #059669;
}

.preview-area {
  margin-top: 2rem;
}

.preview-area.hidden {
  display: none;
}

.preview-area h3 {
  margin-bottom: 1rem;
  color: var(--text);
}

.preview-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
}

.preview-item {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem;
  background: var(--background);
}

.preview-item img,
.preview-item svg {
  width: 100%;
  height: auto;
  max-height: 200px;
  object-fit: contain;
  border-radius: 4px;
  margin-bottom: 0.5rem;
}

.preview-item p {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
  word-break: break-all;
}

.preview-compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.compare-half {
  text-align: center;
}

.compare-half .label {
  font-size: 0.75rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
  color: var(--text-secondary);
}

.compare-half img,
.compare-half svg {
  width: 100%;
  height: 120px;
  object-fit: contain;
  border: 1px solid var(--border);
  border-radius: 4px;
}

.history-section {
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
}

.history-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.history-header h3 {
  color: var(--text);
}

.history-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 1rem;
}

.history-item {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem;
  background: var(--background);
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.history-preview svg {
  width: 100%;
  height: 100px;
  object-fit: contain;
  border-radius: 4px;
  background: white;
}

.history-info p {
  font-size: 0.875rem;
  word-break: break-all;
}

.history-info .date {
  color: var(--text-secondary);
  font-size: 0.75rem;
}

.no-history {
  text-align: center;
  color: var(--text-secondary);
  padding: 2rem;
}

.no-history.hidden {
  display: none;
}

footer {
  text-align: center;
  padding: 2rem;
  color: var(--text-secondary);
  border-top: 1px solid var(--border);
  margin-top: 2rem;
}

.footer-links {
  margin-top: 1rem;
  display: flex;
  gap: 2rem;
  justify-content: center;
  flex-wrap: wrap;
}

.footer-links a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color 0.2s;
}

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

.page-content {
  background: var(--card-bg);
  border-radius: 12px;
  padding: 2rem;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
  max-width: 800px;
  margin: 0 auto;
}

.page-content h1 {
  margin-bottom: 2rem;
  color: var(--text);
}

.page-content h2 {
  margin: 2rem 0 1rem;
  color: var(--text);
}

.page-content p {
  margin-bottom: 1rem;
  color: var(--text-secondary);
}

.page-content ol {
  margin-left: 1.5rem;
  color: var(--text-secondary);
}

.page-content li {
  margin-bottom: 1rem;
}

.faq-item {
  border-bottom: 1px solid var(--border);
  padding: 1.5rem 0;
}

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

.faq-item h3 {
  margin-bottom: 0.5rem;
  color: var(--text);
}

@media (max-width: 1024px) {
  .main-content {
    grid-template-columns: 1fr;
  }
  .sidebar {
    display: none;
  }
}

@media (max-width: 768px) {
  nav {
    flex-direction: column;
    gap: 1rem;
  }
  .nav-links {
    gap: 1rem;
  }
  .hero h1 {
    font-size: 1.75rem;
  }
  .converter {
    padding: 1rem;
  }
  .upload-area {
    padding: 2rem 1rem;
  }
  .presets {
    gap: 0.5rem;
  }
  .preset {
    padding: 0.5rem 1rem;
  }
  .preview-grid {
    grid-template-columns: 1fr;
  }
}