*
{
    box-sizing: border-box;
}



.row::after {
    content: "";
    clear: both;
    display: table;
}

/* For mobile phones: */
[class*="col-"] {
    
    width: 100%;
  }
  body {background-color:pink;}

  @media only screen and (min-width: 768px) {
    .row{display:flex;}
    body {background-color:green;}
    /* For desktop: */
    .col-1 {width: 8.33%;}
    .col-2 {width: 16.66%;}
    .col-3 {width: 25%;}
    .col-4 {width: 33.33%;}
    .col-5 {width: 41.66%;}
    .col-6 {width: 50%;}
    .col-7 {width: 58.33%;}
    .col-8 {width: 66.66%;}
    .col-9 {width: 75%;}
    .col-10 {width: 83.33%;}
    .col-11 {width: 91.66%;}
    .col-12 {width: 100%;}
  }

  @media (min-device-width: 1024px) {body {background-color:pink;}}
@media (min-device-width: 1366px) /*1366px or MORE*/ {body {background-color:green;}}