body {
  font-family: system-ui, sans-serif;
  margin: 0;
  background: #f8fafc;
}
header {
  background: #fff;
  border-bottom: 1px solid #e5e7eb;
  padding: 12px 16px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.card {
  background: white;
  border-radius: 12px;
  padding: 16px;
  box-shadow: 0 10px 20px rgba(0,0,0,.05);
}
button {
  padding: 8px 12px;
  border-radius: 8px;
  border: none;
  background: #0f172a;
  color: white;
  cursor: pointer;
}
button.secondary {
  background: #e5e7eb;
  color: #0f172a;
}