Answers for "css square div"

how to make a square div in css

.square {
    background-color: #000;
    width: 50vw;
    height: 50vw;
}
.square h1 {
    color: #fff;
}
/* It works */

how to make a responsive box in css

.square {
  width: 50%;
}

.square:after {
  content: "";
  display: block;
  padding-bottom: 100%;
}