```css
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: Arial, sans-serif;
  background: #f5f7f6;
  color: #222;
}

.container {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

.card {
  width: 100%;
  max-width: 420px;
  background: #fff;
  padding: 40px 30px;
  border-radius: 20px;
  text-align: center;
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.08);
}

.icon {
  font-size: 45px;
  margin-bottom: 20px;
}

h1 {
  font-size: 28px;
  margin-bottom: 12px;
}

p {
  color: #666;
  margin-bottom: 25px;
  line-height: 1.5;
}

.slug-box {
  background: #f1f3f2;
  padding: 15px;
  border-radius: 12px;
  margin-bottom: 20px;
}

.slug-box span {
  display: block;
  font-size: 12px;
  color: #777;
  margin-bottom: 5px;
}

.slug-box strong {
  font-size: 18px;
}

.whatsapp-button {
  display: block;
  width: 100%;
  padding: 15px 20px;
  border-radius: 12px;
  background: #25D366;
  color: white;
  text-decoration: none;
  font-weight: bold;
  transition: 0.2s;
}

.whatsapp-button:hover {
  transform: translateY(-2px);
  opacity: 0.9;
}

.error {
  color: #d33;
}
```