.modal {
  display: none;
  background: #ddd;
  z-index: 999;
  width: 450px;
  height: 300px;
  margin: 10% auto;
  position: absolute;
  top: 0;
  left: calc((100vw - 450px)/2);
}
#close_modal, #close_modal_error {
  color: #ccc;
  font-size: 40px;
  font-weight: bold;
  border-radius: 50%;
  border: 4px solid #ccc;
  width: 30px;
  height: 30px;
  line-height: 30px;
  text-align: center;
  margin: 10px;
  cursor: pointer;
  float: right;
  transform: rotate(45deg);
  transition: all 0.6s;
  box-sizing: content-box;
}
#close_modal:hover {
    color: #000;
    transform: rotate(135deg);
}
.modal_txt {
    box-shadow: 0 4px 12px rgba(0,0,0,0.2), 0 16px 20px rgba(0,0,0,0.2);
    background: #FFF;
    padding: 30px;
    margin: 15% 10%;
    text-align: center;
}

@media (max-width: 420px) {
    .modal {
        width: auto;
        height: auto;
        left: unset;
    }
}