body {
  font-family: system-ui, sans-serif;
  background: #f4f6f9;
  margin: 0;
  color: #222;
}
header {
  text-align: center;
  background: linear-gradient(135deg, #007bff, #00a2ff);
  color: #fff;
  padding: 20px;
  box-shadow: 0 4px 10px rgba(0,0,0,0.1);
}
footer {
  text-align: center;
  padding: 10px;
  font-size: 13px;
  color: #666;
}
#smtpCards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 15px;
  padding: 20px;
}
.card {
  background: white;
  border-radius: 10px;
  box-shadow: 0 2px 6px rgba(0,0,0,0.1);
  padding: 15px;
  transition: 0.2s;
}
.card:hover { transform: translateY(-4px); }
.warn { text-align: center; color: #999; margin: 30px; }
canvas { display: block; margin: 20px auto; max-width: 900px; }