media query colums to stack on each other when max width is low code example

Example 1: media query min max

@media screen and (min-width: 200px) and (max-width: 640px) {
  .bloc {
    display:block;
    clear:both;
  }
}

Example 2: media query

@media only screen and (max-width: 600px) {
  body {
    // Change size, placement of elements
  }
}