title: In Bootstrap 4, how to change inner $grid-gutter-width depending to breakpoints?
body: <p>I'm currently working on Bootstrap4 in SCSS.</p>
  
  <p>I want to change the inner $grid-gutter-width on smartphone only.</p>
  
  <p>According to _grid.scss</p>
  
  <p><code>$grid-columns: 12 !default;
  $grid-gutter-width: 30px !default;</code></p>
  
  <p>On the bootstrap site, it is sait that :</p>
  
  <blockquote>
    <p>Updated grid sizes, mixins, and variables. Grid gutters now have a Sass map so you can specify specific gutter widths at each breakpoint.</p>
  </blockquote>
  
  <p>I can't find the map and how it can be done.</p>