body {
  background-color: #111;
  color: #fff;
  font-family: Arial, sans-serif;
  display: flex;
  height: 100vh;
  align-items: center;
  justify-content: center;
  margin: 0;
}
.box {
  text-align: center;
  border: 2px solid #00ff99;
  padding: 30px;
  border-radius: 12px;
  box-shadow: 0 0 10px #00ff99;
}
.btn {
  display: inline-block;
  margin-top: 20px;
  padding: 12px 24px;
  background: #00ff99;
  color: #000;
  text-decoration: none;
  font-weight: bold;
  border-radius: 6px;
}
.btn:hover {
  background: #00dd88;
}