:root {
  color-scheme: dark;
  font-family: Inter, system-ui, sans-serif;
}
body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  background: linear-gradient(135deg, #0f172a, #1e293b);
  color: #e2e8f0;
  padding: 24px;
}
.card {
  width: min(92vw, 420px);
  background: rgba(15, 23, 42, 0.92);
  border: 1px solid rgba(148, 163, 184, 0.2);
  border-radius: 18px;
  padding: 28px;
  box-shadow: 0 20px 50px rgba(0,0,0,0.35);
}
.card.wide {
  width: min(92vw, 680px);
}
h1 { margin: 0 0 8px; }
.subtitle { margin: 0 0 20px; color: #94a3b8; line-height: 1.5; }
.calc-form {
  display: grid;
  gap: 14px;
}
label {
  display: grid;
  gap: 6px;
}
label span {
  color: #cbd5e1;
  font-size: 14px;
}
input, select, button {
  width: 100%;
  box-sizing: border-box;
  border-radius: 10px;
  border: 1px solid #334155;
  padding: 12px 14px;
  font-size: 16px;
}
input, select {
  background: #0f172a;
  color: #e2e8f0;
}
button {
  background: #2563eb;
  color: white;
  font-weight: 700;
  cursor: pointer;
}
.result {
  margin-top: 18px;
  padding: 14px;
  border-radius: 10px;
  line-height: 1.6;
}
.success { background: rgba(34, 197, 94, 0.12); color: #86efac; }
.error { background: rgba(239, 68, 68, 0.12); color: #fca5a5; }
.totals {
  margin-top: 16px;
  display: grid;
  gap: 10px;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
}
.totals div {
  background: rgba(59, 130, 246, 0.10);
  border: 1px solid rgba(96, 165, 250, 0.2);
  border-radius: 10px;
  padding: 12px;
}