:root {
  color-scheme: light;
  --bg: #f5f6fa;
  --card: #ffffff;
  --text: #1f2430;
  --muted: #6b7280;
  --accent: #4f46e5;
  --accent-hover: #4338ca;
  --border: #e5e7eb;
  --error: #dc2626;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  justify-content: center;
  padding: 40px 16px;
  min-height: 100vh;
}

.app {
  width: 100%;
  max-width: 480px;
  background: var(--card);
  border-radius: 16px;
  padding: 28px;
  box-shadow: 0 8px 30px rgba(0,0,0,0.06);
}

header h1 {
  margin: 0 0 4px;
  font-size: 1.6rem;
}

.subtitle {
  margin: 0 0 24px;
  color: var(--muted);
  font-size: 0.9rem;
}

#convert-form {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 16px;
}

input[type=file] {
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 0.9rem;
}

button {
  cursor: pointer;
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  background: var(--accent);
  color: white;
  padding: 10px 18px;
  font-weight: 600;
}

button:hover {
  background: var(--accent-hover);
}

button:disabled {
  background: var(--muted);
  cursor: not-allowed;
}

.status {
  font-size: 0.9rem;
  margin: 0 0 12px;
}

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

.hint {
  font-size: 0.8rem;
  color: var(--muted);
  margin: 0;
}