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

body {
  font-family: 'Arial', sans-serif;
  background: #f4f4f4;
  color: #333;
}

header {
  background: #25D366;
  color: #fff;
  padding: 1rem;
  text-align: center;
}

nav a {
  color: #fff;
  margin: 0 1rem;
  text-decoration: none;
  font-weight: bold;
}

nav a:hover {
  text-decoration: underline;
}

section {
  padding: 4rem 2rem;
  max-width: 900px;
  margin: auto;
}

#home {
  background: #e8f5e9;
  text-align: center;
}

h2 {
  margin-bottom: 1rem;
}

ul {
  list-style: none;
}

ul li {
  margin-bottom: 0.5rem;
}

.btn {
  display: inline-block;
  background: #25D366;
  color: #fff;
  padding: 0.75rem 1.5rem;
  margin-top: 1rem;
  text-decoration: none;
  border-radius: 5px;
  transition: background 0.3s;
}

.btn:hover {
  background: #1ebe5d;
}

footer {
  background: #333;
  color: #fff;
  text-align: center;
  padding: 1rem;
  margin-top: 2rem;
}

@media (max-width: 600px) {
  nav a {
    display: block;
    margin: 0.5rem 0;
  }
}