body {
  font-family: system-ui, -apple-system, sans-serif;
  margin: 0;
  padding: 12px;
  background: #f0f2f5;
  color: #1a1a1a;
  line-height: 1.5;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 12px;
}

.checker-container {
  background: white;
  padding: 24px 16px;
  border-radius: 12px;
  box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

h1 {
  text-align: center;
  color: #1a1a1a;
  margin-bottom: 24px;
  font-size: 1.75rem;
}

h2 {
  color: #1a1a1a;
  margin: 0;
  font-size: 1.125rem;
}

.input-section {
  display: flex;
  flex-direction: row;
  gap: 20px;
  margin-bottom: 20px;
}

.input-group {
  flex: 1;
  margin-bottom: 20px;
}

.input-header, .result-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}

label {
  font-weight: 600;
  color: #1a1a1a;
  font-size: 0.9375rem;
}

textarea {
  width: 100%;
  padding: 12px;
  border: 1px solid #e5e7eb;
  border-radius: 8px;
  font-family: ui-monospace, monospace;
  font-size: 14px;
  resize: vertical;
  transition: all 0.2s ease;
  background: #f9fafb;
  min-height: 120px;
  box-sizing: border-box;
}

textarea:focus {
  outline: none;
  border-color: #3b82f6;
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.result-area {
  background: #f8fafc;
}

button {
  border: none;
  border-radius: 6px;
  cursor: pointer;
  font-weight: 500;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  gap: 6px;
}

.check-btn {
  display: block;
  width: 100%;
  max-width: 200px;
  margin: 24px auto;
  padding: 12px 24px;
  background: #3b82f6;
  color: white;
  font-size: 1rem;
  justify-content: center;
}

.check-btn:hover {
  background: #2563eb;
  transform: translateY(-1px);
}

.clear-btn {
  padding: 6px 12px;
  background: #f3f4f6;
  color: #4b5563;
  font-size: 0.875rem;
}

.clear-btn:hover {
  background: #e5e7eb;
}

.copy-btn {
  padding: 6px 12px;
  background: #f0f9ff;
  color: #3b82f6;
  font-size: 0.875rem;
}

.copy-btn:hover {
  background: #e0f2fe;
}

.result-section {
  margin-top: 24px;
  padding-top: 20px;
  border-top: 1px solid #e5e7eb;
}

.btn-icon {
  font-size: 1.125rem;
  line-height: 1;
}

@media (max-width: 768px) {
  body {
    padding: 8px;
  }
  
  .container {
    padding: 8px;
  }
  
  .checker-container {
    padding: 16px 12px;
  }
  
  .input-section {
    flex-direction: column;
  }
  
  .input-group {
    flex: none;
    width: 100%;
  }
  
  h1 {
    font-size: 1.5rem;
    margin-bottom: 20px;
  }
  
  .btn-text {
    display: none;
  }
  
  .btn-icon {
    margin: 0;
  }
  
  .clear-btn, .copy-btn {
    padding: 8px;
    min-width: 32px;
    justify-content: center;
  }
  
  textarea {
    font-size: 16px;
    padding: 10px;
  }
}

@media (max-width: 480px) {
  body {
    padding: 8px;
  }
  
  .container {
    padding: 8px;
  }
  
  textarea {
    min-height: 100px;
  }
}

/* New Styles for Enhanced Features */

.config-section {
  background: #f8fafc;
  padding: 16px;
  border-radius: 8px;
  margin-bottom: 24px;
  border: 1px solid #e2e8f0;
}

.config-section h3 {
  margin: 0 0 16px 0;
  font-size: 1.125rem;
  color: #1e293b;
}

.config-row {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
}

.config-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
  min-width: 200px;
}

.config-group label {
  font-size: 0.875rem;
  color: #374151;
}

.separator-select, .comparison-mode {
  padding: 8px 12px;
  border: 1px solid #d1d5db;
  border-radius: 6px;
  background: white;
  font-size: 0.875rem;
  cursor: pointer;
  transition: border-color 0.2s ease;
}

.separator-select:focus, .comparison-mode:focus {
  outline: none;
  border-color: #3b82f6;
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.custom-separator {
  padding: 8px 12px;
  border: 1px solid #d1d5db;
  border-radius: 6px;
  font-size: 0.875rem;
  margin-top: 8px;
  transition: border-color 0.2s ease;
}

.custom-separator:focus {
  outline: none;
  border-color: #3b82f6;
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.preview-area {
  margin-top: 12px;
  padding: 12px;
  background: #f1f5f9;
  border-radius: 6px;
  border: 1px solid #e2e8f0;
  font-size: 0.875rem;
}

.preview-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
  font-weight: 500;
  color: #475569;
}

.item-count {
  font-size: 0.75rem;
  color: #64748b;
  background: #e2e8f0;
  padding: 2px 8px;
  border-radius: 4px;
}

.preview-content {
  font-family: ui-monospace, monospace;
  font-size: 0.8125rem;
  color: #334155;
  white-space: pre-wrap;
  max-height: 150px;
  overflow-y: auto;
}

.field-section {
  background: #f0f9ff;
  padding: 16px;
  border-radius: 8px;
  margin-bottom: 24px;
  border: 1px solid #bae6fd;
}

.field-section h3 {
  margin: 0 0 8px 0;
  font-size: 1.125rem;
  color: #0c4a6e;
}

.field-help {
  margin: 0 0 16px 0;
  font-size: 0.875rem;
  color: #475569;
}

.field-selection {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
}

.field-checkboxes {
  flex: 1;
  min-width: 200px;
}

.field-checkbox {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
  font-size: 0.875rem;
}

.field-checkbox input[type="checkbox"] {
  width: 16px;
  height: 16px;
  cursor: pointer;
}

.field-checkbox label {
  cursor: pointer;
  font-weight: normal;
}

.field-sample {
  flex: 1;
  min-width: 250px;
  padding: 12px;
  background: white;
  border-radius: 6px;
  border: 1px solid #e2e8f0;
}

.sample-content {
  font-family: ui-monospace, monospace;
  font-size: 0.8125rem;
  margin-top: 8px;
  padding: 8px;
  background: #f8fafc;
  border-radius: 4px;
  color: #334155;
}

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

.export-btn {
  padding: 6px 12px;
  background: #f0fdf4;
  color: #16a34a;
  font-size: 0.875rem;
}

.export-btn:hover {
  background: #dcfce7;
}

/* Mobile Responsiveness for New Features */
@media (max-width: 768px) {
  .config-row {
    flex-direction: column;
    gap: 16px;
  }
  
  .config-group {
    min-width: auto;
  }
  
  .field-selection {
    flex-direction: column;
    gap: 16px;
  }
  
  .field-sample {
    min-width: auto;
  }
  
  .result-actions {
    flex-direction: column;
    gap: 8px;
  }
  
  .result-actions .copy-btn,
  .result-actions .export-btn {
    justify-content: center;
  }
}

@media (max-width: 480px) {
  .config-section,
  .field-section {
    padding: 12px;
  }
  
  .preview-area {
    padding: 8px;
  }
  
  .preview-content {
    font-size: 0.75rem;
  }
}