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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #f0f4f8;
  color: #1a202c;
  min-height: 100vh;
  padding: 2rem 1rem;
}

.container {
  max-width: 680px;
  margin: 0 auto;
}

h1 {
  text-align: center;
  font-size: 1.6rem;
  margin-bottom: 1.5rem;
  color: #2d3748;
}

.card {
  background: #fff;
  border-radius: 10px;
  padding: 1.25rem;
  margin-bottom: 1rem;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.08);
}

label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  color: #4a5568;
  margin-bottom: 0.5rem;
}

textarea {
  width: 100%;
  border: 1px solid #e2e8f0;
  border-radius: 6px;
  padding: 0.75rem;
  font-size: 0.95rem;
  font-family: "SFMono-Regular", Consolas, monospace;
  resize: vertical;
  transition: border-color 0.15s;
  line-height: 1.5;
}

textarea:focus {
  outline: none;
  border-color: #4299e1;
  box-shadow: 0 0 0 3px rgba(66, 153, 225, 0.2);
}

textarea[readonly] {
  background: #f7fafc;
}

.button-row {
  display: flex;
  gap: 0.5rem;
  margin-top: 0.75rem;
  flex-wrap: wrap;
}

.btn {
  padding: 0.5rem 1.1rem;
  border: none;
  border-radius: 6px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s;
}

.btn:active {
  transform: scale(0.97);
}

.btn.primary {
  background: #4299e1;
  color: #fff;
}

.btn.primary:hover {
  background: #3182ce;
}

.btn.secondary {
  background: #edf2f7;
  color: #4a5568;
}

.btn.secondary:hover {
  background: #e2e8f0;
}

.error {
  background: #fff5f5;
  border: 1px solid #fc8181;
  color: #c53030;
  border-radius: 6px;
  padding: 0.75rem 1rem;
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

.hidden {
  display: none;
}