Add modern CSS styling

assets/style.css

@@ -0,0 +1,455 @@
+/* Modern TTS UI - Lightweight & Beautiful */
+:root {
+  --primary: #6366f1;
+  --primary-dark: #4f46e5;
+  --secondary: #8b5cf6;
+  --success: #10b981;
+  --warning: #f59e0b;
+  --danger: #ef4444;
+  --bg: #0f172a;
+  --bg-light: #1e293b;
+  --surface: #334155;
+  --text: #f1f5f9;
+  --text-muted: #94a3b8;
+  --border: #475569;
+  --glass: rgba(255, 255, 255, 0.05);
+  --shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
+  --radius: 16px;
+}
+
+* {
+  margin: 0;
+  padding: 0;
+  box-sizing: border-box;
+}
+
+body {
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Inter', sans-serif;
+  background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
+  color: var(--text);
+  line-height: 1.6;
+  min-height: 100vh;
+  padding: 20px;
+  overflow-x: hidden;
+}
+
+/* Header */
+h1 {
+  font-size: clamp(1.5rem, 5vw, 2.5rem);
+  font-weight: 700;
+  background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
+  -webkit-background-clip: text;
+  -webkit-text-fill-color: transparent;
+  background-clip: text;
+  margin-bottom: 8px;
+  text-align: center;
+}
+
+.subtitle {
+  text-align: center;
+  color: var(--text-muted);
+  margin-bottom: 32px;
+  font-size: 0.95rem;
+}
+
+/* Layout */
+.row {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
+  gap: 20px;
+  margin-bottom: 20px;
+}
+
+.col {
+  background: var(--glass);
+  backdrop-filter: blur(10px);
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  padding: 24px;
+  box-shadow: var(--shadow);
+  transition: transform 0.2s, box-shadow 0.2s;
+}
+
+.col:hover {
+  transform: translateY(-2px);
+  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.4);
+}
+
+/* Fieldset */
+fieldset {
+  border: none;
+  margin-bottom: 20px;
+  padding: 0;
+}
+
+legend {
+  font-size: 1.1rem;
+  font-weight: 600;
+  color: var(--primary);
+  margin-bottom: 12px;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+legend::before {
+  content: "▶";
+  font-size: 0.8rem;
+  color: var(--secondary);
+}
+
+/* Inputs */
+label {
+  display: block;
+  margin: 12px 0 6px;
+  color: var(--text);
+  font-size: 0.9rem;
+  font-weight: 500;
+}
+
+input[type="range"] {
+  width: 100%;
+  height: 6px;
+  background: linear-gradient(90deg, var(--primary), var(--secondary));
+  border-radius: 10px;
+  outline: none;
+  opacity: 0.8;
+  transition: opacity 0.2s;
+  cursor: pointer;
+}
+
+input[type="range"]:hover {
+  opacity: 1;
+}
+
+input[type="range"]::-webkit-slider-thumb {
+  appearance: none;
+  width: 18px;
+  height: 18px;
+  background: white;
+  border-radius: 50%;
+  cursor: pointer;
+  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
+  transition: transform 0.2s;
+}
+
+input[type="range"]::-webkit-slider-thumb:hover {
+  transform: scale(1.2);
+}
+
+input[type="range"]::-moz-range-thumb {
+  width: 18px;
+  height: 18px;
+  background: white;
+  border-radius: 50%;
+  cursor: pointer;
+  border: none;
+  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
+}
+
+input[type="text"],
+input[type="file"],
+select {
+  width: 100%;
+  padding: 10px 14px;
+  background: var(--bg-light);
+  border: 1px solid var(--border);
+  border-radius: 10px;
+  color: var(--text);
+  font-size: 0.95rem;
+  transition: all 0.2s;
+}
+
+input[type="text"]:focus,
+select:focus {
+  outline: none;
+  border-color: var(--primary);
+  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
+}
+
+input[type="file"]::file-selector-button {
+  padding: 8px 16px;
+  background: var(--primary);
+  color: white;
+  border: none;
+  border-radius: 8px;
+  cursor: pointer;
+  margin-right: 12px;
+  transition: background 0.2s;
+}
+
+input[type="file"]::file-selector-button:hover {
+  background: var(--primary-dark);
+}
+
+textarea {
+  width: 100%;
+  min-height: 120px;
+  padding: 12px;
+  background: var(--bg-light);
+  border: 1px solid var(--border);
+  border-radius: 10px;
+  color: var(--text);
+  font-family: inherit;
+  font-size: 0.95rem;
+  resize: vertical;
+  transition: all 0.2s;
+}
+
+textarea:focus {
+  outline: none;
+  border-color: var(--primary);
+  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
+}
+
+/* Checkboxes & Radio */
+input[type="checkbox"],
+input[type="radio"] {
+  width: 18px;
+  height: 18px;
+  margin-right: 8px;
+  cursor: pointer;
+  accent-color: var(--primary);
+}
+
+/* Buttons */
+button {
+  padding: 12px 24px;
+  background: linear-gradient(135deg, var(--primary), var(--secondary));
+  color: white;
+  border: none;
+  border-radius: 10px;
+  font-weight: 600;
+  font-size: 0.95rem;
+  cursor: pointer;
+  transition: all 0.2s;
+  box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
+  position: relative;
+  overflow: hidden;
+}
+
+button::before {
+  content: "";
+  position: absolute;
+  top: 0;
+  left: -100%;
+  width: 100%;
+  height: 100%;
+  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
+  transition: left 0.5s;
+}
+
+button:hover::before {
+  left: 100%;
+}
+
+button:hover {
+  transform: translateY(-2px);
+  box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
+}
+
+button:active {
+  transform: translateY(0);
+}
+
+button:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+  transform: none;
+}
+
+button.secondary {
+  background: var(--surface);
+  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
+}
+
+button.secondary:hover {
+  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.3);
+}
+
+/* Chips */
+.chip {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  padding: 6px 14px;
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: 999px;
+  font-size: 0.85rem;
+  font-weight: 500;
+  margin: 4px;
+  transition: all 0.2s;
+}
+
+.chip.active {
+  background: linear-gradient(135deg, var(--primary), var(--secondary));
+  border-color: transparent;
+  color: white;
+}
+
+.chip::before {
+  content: "●";
+  font-size: 0.6rem;
+}
+
+.chip.success::before { color: var(--success); }
+.chip.warning::before { color: var(--warning); }
+.chip.danger::before { color: var(--danger); }
+
+/* Audio Player */
+audio {
+  width: 100%;
+  margin: 16px 0;
+  border-radius: 10px;
+  filter: hue-rotate(200deg);
+}
+
+/* Download Link */
+a {
+  display: inline-block;
+  padding: 12px 24px;
+  background: var(--success);
+  color: white;
+  text-decoration: none;
+  border-radius: 10px;
+  font-weight: 600;
+  transition: all 0.2s;
+  box-shadow: 0 4px 12px rgba(16, 185, 129, 0.3);
+}
+
+a:hover {
+  background: #059669;
+  transform: translateY(-2px);
+  box-shadow: 0 6px 20px rgba(16, 185, 129, 0.4);
+}
+
+/* Log Box */
+.mono {
+  font-family: 'SF Mono', 'Monaco', 'Consolas', monospace;
+  font-size: 0.8rem;
+  line-height: 1.6;
+  color: var(--text-muted);
+}
+
+#log {
+  background: var(--bg);
+  border: 1px solid var(--border);
+  border-radius: 10px;
+  padding: 12px;
+  max-height: 200px;
+  overflow-y: auto;
+  white-space: pre-wrap;
+  word-wrap: break-word;
+}
+
+#log::-webkit-scrollbar {
+  width: 8px;
+}
+
+#log::-webkit-scrollbar-track {
+  background: var(--bg-light);
+  border-radius: 10px;
+}
+
+#log::-webkit-scrollbar-thumb {
+  background: var(--primary);
+  border-radius: 10px;
+}
+
+/* Grid Layouts */
+.grid {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 12px;
+}
+
+/* Utilities */
+.hidden { display: none !important; }
+.muted { color: var(--text-muted); }
+.text-center { text-align: center; }
+.mt-1 { margin-top: 8px; }
+.mt-2 { margin-top: 16px; }
+.mb-1 { margin-bottom: 8px; }
+.mb-2 { margin-bottom: 16px; }
+
+/* Responsive */
+@media (max-width: 768px) {
+  .row {
+    grid-template-columns: 1fr;
+  }
+
+  .grid {
+    grid-template-columns: 1fr;
+  }
+
+  .col {
+    padding: 16px;
+  }
+
+  h1 {
+    font-size: 1.75rem;
+  }
+}
+
+/* Animations */
+@keyframes fadeIn {
+  from {
+    opacity: 0;
+    transform: translateY(10px);
+  }
+  to {
+    opacity: 1;
+    transform: translateY(0);
+  }
+}
+
+.col {
+  animation: fadeIn 0.5s ease-out;
+}
+
+.col:nth-child(1) { animation-delay: 0.1s; }
+.col:nth-child(2) { animation-delay: 0.2s; }
+.col:nth-child(3) { animation-delay: 0.3s; }
+
+/* Loading Spinner */
+@keyframes spin {
+  to { transform: rotate(360deg); }
+}
+
+.spinner {
+  display: inline-block;
+  width: 16px;
+  height: 16px;
+  border: 2px solid rgba(255, 255, 255, 0.3);
+  border-top-color: white;
+  border-radius: 50%;
+  animation: spin 0.6s linear infinite;
+}
+
+/* Toast/Status Messages */
+.status-message {
+  padding: 12px 20px;
+  border-radius: 10px;
+  margin: 12px 0;
+  font-weight: 500;
+  animation: fadeIn 0.3s ease-out;
+}
+
+.status-message.success {
+  background: rgba(16, 185, 129, 0.2);
+  border: 1px solid var(--success);
+  color: var(--success);
+}
+
+.status-message.error {
+  background: rgba(239, 68, 68, 0.2);
+  border: 1px solid var(--danger);
+  color: var(--danger);
+}
+
+.status-message.info {
+  background: rgba(99, 102, 241, 0.2);
+  border: 1px solid var(--primary);
+  color: var(--primary);
+}