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

:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-light: #dbeafe;
  --bg: #f8fafc;
  --card-bg: #ffffff;
  --text: #1e293b;
  --text-secondary: #64748b;
  --border: #e2e8f0;
  --error: #ef4444;
  --error-bg: #fef2f2;
  --success: #22c55e;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(0,0,0,0.08), 0 4px 12px rgba(0,0,0,0.05);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 640px;
  margin: 0 auto;
  padding: 24px 16px 48px;
}

header {
  text-align: center;
  margin-bottom: 24px;
}

header h1 {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--text);
}

.subtitle {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

.card {
  background: var(--card-bg);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}

.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 6px;
}

.form-group input,
.form-group select,
.form-group textarea {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 1rem;
  color: var(--text);
  background: #fff;
  transition: border-color 0.15s, box-shadow 0.15s;
  -webkit-appearance: none;
  appearance: none;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-light);
}

.form-group select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' fill='%2364748b' viewBox='0 0 16 16'%3E%3Cpath d='M1.646 4.646a.5.5 0 0 1 .708 0L8 10.293l5.646-5.647a.5.5 0 0 1 .708.708l-6 6a.5.5 0 0 1-.708 0l-6-6a.5.5 0 0 1 0-.708z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  padding-right: 36px;
}

.form-group textarea {
  resize: vertical;
  min-height: 120px;
  font-family: inherit;
  line-height: 1.5;
}

.char-count {
  text-align: right;
  font-size: 0.75rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

.hint {
  font-size: 0.75rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

.hint code {
  background: #f1f5f9;
  padding: 1px 4px;
  border-radius: 4px;
  font-family: "SF Mono", Monaco, monospace;
}

.form-row {
  display: flex;
  gap: 16px;
}

.form-group.half {
  flex: 1;
}

.form-group input[type="range"] {
  padding: 0;
  margin-top: 4px;
  cursor: pointer;
}

.range-value {
  display: inline-block;
  font-size: 0.8125rem;
  color: var(--text-secondary);
  margin-top: 2px;
  min-width: 36px;
}

.btn-primary,
.btn-secondary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  width: 100%;
  padding: 12px 20px;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s;
  -webkit-tap-highlight-color: transparent;
}

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

.btn-primary:hover:not(:disabled) {
  background: var(--primary-dark);
}

.btn-primary:active:not(:disabled) {
  transform: scale(0.98);
}

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

.btn-secondary {
  background: var(--bg);
  color: var(--primary);
  border: 1px solid var(--border);
}

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

.spinner {
  display: inline-block;
  width: 18px;
  height: 18px;
  border: 2px solid rgba(255,255,255,0.3);
  border-top-color: #fff;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

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

.hidden {
  display: none !important;
}

.error-box {
  margin-top: 16px;
  padding: 12px 16px;
  background: var(--error-bg);
  border: 1px solid #fecaca;
  border-radius: 8px;
  color: var(--error);
  font-size: 0.875rem;
}

.result-area {
  margin-top: 24px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.audio-wrapper {
  margin-bottom: 16px;
}

.audio-wrapper audio {
  width: 100%;
  border-radius: 8px;
}

footer {
  text-align: center;
  margin-top: 32px;
}

footer p {
  font-size: 0.8125rem;
  color: var(--text-secondary);
}

/* Desktop */
@media (min-width: 640px) {
  .container {
    padding-top: 48px;
  }

  header h1 {
    font-size: 2rem;
  }

  .card {
    padding: 32px;
  }
}

/* Small mobile tweaks */
@media (max-width: 360px) {
  .card {
    padding: 16px;
  }

  header h1 {
    font-size: 1.5rem;
  }
}