:root {
  color-scheme: light dark;
  font-family:
    "Inter",
    system-ui,
    -apple-system,
    sans-serif;
  line-height: 1.5;
}
body {
  margin: 0;
  display: flex;
  min-height: 100vh;
  background: radial-gradient(circle at top, #fdfbfb, #ebedee);
  justify-content: center;
  align-items: center;
  padding: 2rem;
}
.card {
  background: rgba(255, 255, 255, 0.95);
  border-radius: 18px;
  box-shadow: 0 20px 45px rgba(15, 23, 42, 0.12);
  padding: 2.5rem;
  max-width: 420px;
  width: 100%;
}
h1 {
  margin-top: 0;
  font-size: 1.75rem;
  color: #0f172a;
}
p {
  margin: 0.5rem 0 1.5rem;
  color: #475569;
}
.price {
  font-size: 1.5rem;
  font-weight: 600;
  color: #2563eb;
  margin-bottom: 1.5rem;
}
form {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}
label {
  font-weight: 600;
  color: #1e293b;
}
input[type="number"] {
  width: 100%;
  padding: 0.75rem 1rem;
  border-radius: 12px;
  border: 1px solid #cbd5f5;
  font-size: 1rem;
}
button {
  background: linear-gradient(135deg, #2563eb, #7c3aed);
  border: none;
  border-radius: 12px;
  color: #fff;
  font-size: 1rem;
  font-weight: 600;
  padding: 0.9rem 1.2rem;
  cursor: pointer;
  transition:
    transform 0.15s ease,
    box-shadow 0.15s ease;
}
button:hover:not([disabled]) {
  transform: translateY(-1px);
  box-shadow: 0 12px 30px rgba(37, 99, 235, 0.25);
}
button[disabled] {
  opacity: 0.65;
  cursor: wait;
}
#message {
  min-height: 1.5rem;
  color: #dc2626;
  font-size: 0.95rem;
}