/* CSS Custom Properties */
:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f5f5f5;
  --bg-tertiary: #e8e8e8;
  --text-primary: #1a1a1a;
  --text-secondary: #666666;
  --accent: #4a90d9;
  --accent-hover: #357abd;
  --border: #ddd;
  --shadow: rgba(0, 0, 0, 0.1);
  --drop-zone-bg: #f9f9f9;
  --drop-zone-border: #ccc;
  --success: #28a745;
  --error: #dc3545;
}

[data-theme="dark"] {
  --bg-primary: #1a1a1a;
  --bg-secondary: #2d2d2d;
  --bg-tertiary: #404040;
  --text-primary: #f0f0f0;
  --text-secondary: #aaaaaa;
  --accent: #5ba3ec;
  --accent-hover: #7bb8f5;
  --border: #444;
  --shadow: rgba(0, 0, 0, 0.3);
  --drop-zone-bg: #252525;
  --drop-zone-border: #555;
}

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

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background-color 0.3s, color 0.3s;
}

/* Container */
.container {
  max-width: 700px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

/* Header */
header {
  text-align: center;
  margin-bottom: 2rem;
  position: relative;
}

h1 {
  margin: 0 0 0.5rem;
  font-size: 2rem;
  font-weight: 700;
}

.subtitle {
  color: var(--text-secondary);
  margin: 0;
}

/* Theme Toggle */
.theme-toggle {
  position: absolute;
  top: 0;
  right: 0;
  background: none;
  border: none;
  cursor: pointer;
  font-size: 1.5rem;
  padding: 0.5rem;
  color: var(--text-primary);
}

.theme-toggle .icon-moon {
  display: none;
}

[data-theme="dark"] .theme-toggle .icon-sun {
  display: none;
}

[data-theme="dark"] .theme-toggle .icon-moon {
  display: inline;
}

/* Section Styling */
section {
  margin-bottom: 2rem;
}

h2 {
  font-size: 1.1rem;
  font-weight: 600;
  margin: 0 0 1rem;
  color: var(--text-primary);
}

/* Upload Section */
.drop-zone {
  border: 2px dashed var(--drop-zone-border);
  border-radius: 12px;
  padding: 3rem 2rem;
  text-align: center;
  background-color: var(--drop-zone-bg);
  cursor: pointer;
  transition: border-color 0.2s, background-color 0.2s;
}

.drop-zone:hover,
.drop-zone.drag-over {
  border-color: var(--accent);
  background-color: var(--bg-secondary);
}

.drop-zone-content {
  pointer-events: none;
}

.upload-icon {
  font-size: 3rem;
  display: block;
  margin-bottom: 1rem;
}

.drop-zone p {
  margin: 0.5rem 0;
  color: var(--text-secondary);
}

.or {
  font-size: 0.9rem;
}

.file-input-label {
  display: inline-block;
  margin-top: 0.5rem;
  padding: 0.6rem 1.5rem;
  background-color: var(--accent);
  color: white;
  border-radius: 6px;
  cursor: pointer;
  font-weight: 500;
  transition: background-color 0.2s;
  pointer-events: auto;
}

.file-input-label:hover {
  background-color: var(--accent-hover);
}

.file-name {
  text-align: center;
  margin-top: 1rem;
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.file-name.has-file {
  color: var(--success);
  font-weight: 500;
}

/* Configuration Section */
.config-section {
  background-color: var(--bg-secondary);
  padding: 1.5rem;
  border-radius: 12px;
}

.config-group {
  margin-bottom: 1.5rem;
}

.config-group:last-child {
  margin-bottom: 0;
}

.config-group label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 500;
}

.config-help {
  margin: 0.5rem 0 0;
  font-size: 0.85rem;
  color: var(--text-secondary);
}

/* Range Slider */
input[type="range"] {
  width: 100%;
  height: 6px;
  border-radius: 3px;
  background: var(--bg-tertiary);
  outline: none;
  -webkit-appearance: none;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  transition: transform 0.1s;
}

input[type="range"]::-webkit-slider-thumb:hover {
  transform: scale(1.1);
}

input[type="range"]::-moz-range-thumb {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  border: none;
}

/* Select Dropdown */
select {
  width: 100%;
  padding: 0.75rem;
  font-size: 1rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  cursor: pointer;
}

select:focus {
  outline: none;
  border-color: var(--accent);
}

/* Preview Section */
.preview-box {
  background-color: var(--bg-secondary);
  padding: 1.5rem;
  border-radius: 12px;
  font-size: 1.1rem;
  line-height: 1.8;
}

.preview-box p {
  margin: 0;
}

.preview-box b {
  font-weight: var(--preview-bold-weight, 700);
}

/* Download Section */
.download-section {
  text-align: center;
}

.convert-btn {
  display: inline-block;
  padding: 1rem 2.5rem;
  font-size: 1.1rem;
  font-weight: 600;
  color: white;
  background-color: var(--accent);
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background-color 0.2s, transform 0.1s, opacity 0.2s;
}

.convert-btn:hover:not(:disabled) {
  background-color: var(--accent-hover);
  transform: translateY(-1px);
}

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

.status-message {
  margin-top: 1rem;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.status-message.error {
  color: var(--error);
}

.status-message.success {
  color: var(--success);
}

/* Footer */
footer {
  text-align: center;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
}

footer p {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin: 0;
}

/* Responsive */
@media (max-width: 600px) {
  .container {
    padding: 1.5rem 1rem;
  }

  h1 {
    font-size: 1.6rem;
  }

  .drop-zone {
    padding: 2rem 1rem;
  }

  .preview-box {
    font-size: 1rem;
    line-height: 1.7;
  }
}