:root {
  --bg: #f5f7fb;
  --panel: #ffffff;
  --text: #0f172a;
  --sub: #475569;
  --primary: #0ea5e9;
  --primary-strong: #0284c7;
  --border: #dbe4f0;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  background: radial-gradient(circle at 20% 0%, #e0f2fe 0, transparent 45%), var(--bg);
  color: var(--text);
}

.shell {
  max-width: 980px;
  margin: 0 auto;
  padding: 24px;
  display: grid;
  gap: 16px;
}

.hero h1 { margin: 0 0 8px; }
.hero p { margin: 0; color: var(--sub); }

.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 16px;
}

.grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(120px, 1fr));
  gap: 10px;
  align-items: end;
}

label {
  display: grid;
  gap: 6px;
  font-size: 14px;
}

input, select, button {
  border-radius: 10px;
  border: 1px solid #cdd8e5;
  padding: 10px;
  font-size: 14px;
}

button {
  background: var(--primary);
  color: white;
  border: none;
  cursor: pointer;
}
button:hover { background: var(--primary-strong); }
button:disabled { opacity: .45; cursor: not-allowed; }

.hint { color: var(--sub); min-height: 20px; }
pre {
  background: #0f172a;
  color: #d1fae5;
  padding: 12px;
  border-radius: 10px;
  overflow-x: auto;
}
.row { display: flex; gap: 10px; flex-wrap: wrap; }

@media (max-width: 860px) {
  .grid { grid-template-columns: repeat(2, minmax(120px, 1fr)); }
}

@media (max-width: 520px) {
  .shell { padding: 12px; }
  .grid { grid-template-columns: 1fr; }
}