.modal{
  display:none;
  position:fixed;
  top:0; left:0;
  width:100%; height:100%;
  background:rgba(0,0,0,0.5);
  justify-content:center;
  align-items:center;
  z-index:999;
}

.modal-content{
  background:#fff;
  padding:20px;
  border-radius:12px;
  max-width:400px;
  text-align:center;
  box-shadow:0 10px 25px rgba(0,0,0,.2);
}

.modal-content button{
  margin-top:15px;
  background:#007bff;
  color:#fff;
  border:none;
  padding:10px 20px;
  border-radius:8px;
  cursor:pointer;
}

.faltante{
  border:2px solid red;
  background:#fff5f5;
}