@media (max-width: 768px) {
  .main-box {
    padding: 20px;
    width: 90%;
  }

  input, button {
    font-size: 16px;
    padding: 10px 12px;
    width: 100%;
  }
}
@media (max-width: 480px) {
  .main-box {
    padding: 15px;
    width: 95%;
  }

  input, button {
    font-size: 15px;
    padding: 9px 11px;
  }
}

@media (max-width: 320px) {
  .main-box {
    padding: 12px;
    width: 98%;
  }

  input, button {
    font-size: 14px;
    padding: 8px 10px;
  }
}