* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Inter, Segoe UI, Roboto, Arial, sans-serif;
  background: linear-gradient(135deg, #1f2937, #0f766e, #1d4ed8);
  color: #0f172a;
}

.app {
  display: grid;
  place-items: center;
  padding: 24px;
  min-height: 100vh;
}

.card {
  width: min(760px, 100%);
  background: #f8fafc;
  border-radius: 16px;
  padding: 24px;
  box-shadow: 0 20px 50px rgba(2, 6, 23, 0.35);
}

h1 {
  margin: 0 0 8px;
  font-size: 2rem;
}

.subtitle {
  margin: 0 0 20px;
  color: #334155;
}

label {
  display: block;
  margin-bottom: 8px;
  font-weight: 600;
}

textarea {
  width: 100%;
  border: 1px solid #cbd5e1;
  border-radius: 10px;
  padding: 12px;
  resize: vertical;
  font-size: 1rem;
  margin-bottom: 14px;
}

.row {
  margin-bottom: 18px;
}

input[type="range"] {
  width: 100%;
}

button {
  width: 100%;
  border: none;
  border-radius: 10px;
  background: #0f766e;
  color: #f8fafc;
  font-size: 1rem;
  padding: 12px 14px;
  cursor: pointer;
  font-weight: 700;
}

button:hover {
  background: #0b5f58;
}

button:disabled {
  opacity: 0.7;
  cursor: wait;
}

.response {
  margin-top: 18px;
  background: #eef2ff;
  border: 1px solid #c7d2fe;
  border-radius: 10px;
  padding: 14px;
  white-space: pre-wrap;
  line-height: 1.45;
}

.error {
  margin-top: 14px;
  color: #b91c1c;
  font-weight: 600;
}

.hidden {
  display: none;
}