* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 24px;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: radial-gradient(circle at top, #203a43, #0f2027);
  color: #eef3ff;
}

.card {
  width: min(640px, 94vw);
  padding: 24px;
  border-radius: 18px;
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.14);
  box-shadow: 0 16px 40px rgba(0,0,0,0.45);
}

h1 {
  margin: 0 0 8px;
  text-align: center;
}

.hint {
  margin: 0 0 16px;
  text-align: center;
  opacity: 0.85;
}

.label {
  display: block;
  margin-bottom: 8px;
  opacity: 0.9;
}

.row {
  display: flex;
  gap: 10px;
}

#cash {
  flex: 1;
  padding: 12px 14px;
  border-radius: 12px;
  border: 1px solid rgba(255,255,255,0.18);
  background: rgba(0,0,0,0.25);
  color: #eef3ff;
  outline: none;
}

#purchase-btn {
  padding: 12px 14px;
  border: none;
  border-radius: 12px;
  cursor: pointer;
  font-weight: 800;
  color: #0f2027;
  background: linear-gradient(90deg, #a1ffce, #faffd1);
}

#purchase-btn:active { transform: scale(0.98); }

.output {
  margin: 16px 0 0;
  padding: 12px 14px;
  border-radius: 12px;
  background: rgba(0,0,0,0.22);
  border: 1px solid rgba(255,255,255,0.12);
  min-height: 48px;
  display: grid;
  align-items: center;
  font-weight: 700;
}