.modal {
  display: none;
  position: fixed;
  top: 0; left: 0;
  width: 100%; height: 100%;
  background-color: rgba(0, 0, 0, 0.5);
  z-index: 9999;
}

.modal-content {
  background: #fff;
  margin: 100px auto;
  padding: 20px;
  width: 90%;
  max-width: 400px;
  border-radius: 8px;
  text-align: center;
  box-shadow: 0 2px 8px rgba(0,0,0,0.2);
}