@media screen and (max-width: 500px) {
    .col-md-4 {
    width: 100%;
    }
  }
  @media screen and (max-width: 900px) {
    .col-md-4 {
    width: 100%;
    }
  }
  .container {
    font-family: arial;
    font-size: 24px;
    margin: 25px;
    width: 350px;
    height: 200px;
    outline: dashed 1px black;
    /* Setup */
    position: relative;
  }
  
  .child {
    width: 50px;
    height: 50px;
    background-color: red;
    /* Center vertically and horizontally */
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
  }