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

:root {
  --primary: #6366f1;
  --primary-hover: #4f46e5;
  --success: #10b981;
  --success-hover: #059669;
  --secondary: #64748b;
  --secondary-hover: #475569;
  --error: #ef4444;
  --bg: #f8fafc;
  --card-bg: #ffffff;
  --text: #1e293b;
  --text-light: #64748b;
  --border: #e2e8f0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem 1rem;
}

header {
  text-align: center;
  margin-bottom: 2rem;
}

header h1 {
  font-size: 2rem;
  font-weight: 700;
  color: var(--text);
}

.subtitle {
  color: var(--text-light);
  margin-top: 0.5rem;
}

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

/* Upload Zone */
.upload-zone {
  border: 2px dashed var(--border);
  border-radius: 0.75rem;
  padding: 3rem 2rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s;
}

.upload-zone:hover,
.upload-zone.dragover {
  border-color: var(--primary);
  background: rgba(99, 102, 241, 0.05);
}

.upload-content p {
  color: var(--text-light);
  margin-top: 1rem;
}

.upload-icon {
  width: 4rem;
  height: 4rem;
  color: var(--text-light);
}

.hint {
  font-size: 0.875rem;
  margin-top: 0.5rem !important;
}

.link-btn {
  background: none;
  border: none;
  color: var(--primary);
  cursor: pointer;
  font-size: inherit;
  text-decoration: underline;
}

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

/* Preview Section */
.preview-section {
  margin-top: 1.5rem;
}

.preview-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

.preview-box h3 {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-light);
  margin-bottom: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.preview-img-wrap {
  background: #f1f5f9;
  border-radius: 0.5rem;
  overflow: hidden;
  position: relative;
  min-height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.preview-img-wrap img {
  max-width: 100%;
  max-height: 400px;
  object-fit: contain;
}

.preview-img-wrap.checkerboard {
  background-image: 
    linear-gradient(45deg, #e2e8f0 25%, transparent 25%),
    linear-gradient(-45deg, #e2e8f0 25%, transparent 25%),
    linear-gradient(45deg, transparent 75%, #e2e8f0 75%),
    linear-gradient(-45deg, transparent 75%, #e2e8f0 75%);
  background-size: 16px 16px;
  background-position: 0 0, 0 8px, 8px -8px, -8px 0px;
}

.placeholder {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-light);
  font-size: 0.875rem;
}

.placeholder.hidden {
  display: none;
}

/* Actions */
.actions {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  margin-top: 1.5rem;
  flex-wrap: wrap;
}

.btn {
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: 0.5rem;
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

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

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

.btn.primary:disabled {
  background: var(--secondary);
  cursor: not-allowed;
}

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

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

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

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

.btn-loading {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.spinner {
  width: 1.25rem;
  height: 1.25rem;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

.hidden {
  display: none !important;
}

/* Error */
.error-msg {
  margin-top: 1rem;
  padding: 0.75rem 1rem;
  background: #fef2f2;
  border: 1px solid #fecaca;
  border-radius: 0.5rem;
  color: var(--error);
  text-align: center;
  font-size: 0.875rem;
}

/* Footer */
footer {
  margin-top: 2rem;
  text-align: center;
  color: var(--text-light);
  font-size: 0.75rem;
}

/* Mobile */
@media (max-width: 640px) {
  .preview-grid {
    grid-template-columns: 1fr;
  }

  header h1 {
    font-size: 1.5rem;
  }

  .actions {
    flex-direction: column;
  }

  .btn {
    width: 100%;
    justify-content: center;
  }
}