body {
  background:#111; color:#fff; font-family:Arial,sans-serif;
  text-align:center; padding-top:20vh;
}
.gate-box {
  background:#222; display:inline-block; padding:2rem 3rem;
  border-radius:12px; box-shadow:0 0 10px rgba(0,0,0,0.5);
}
button {
  margin-top:1.5rem; background:#4caf50; color:white; border:none;
  padding:0.8rem 1.5rem; font-size:1rem; border-radius:6px; cursor:pointer;
}
button:hover { background:#43a047; }