Simple SASS Grid - webdesign.tutsplus.com/pt/tutorials/a-simple-responsive-grid-made-even-better-with-sass--cms-21540

grid.scss

@import "variables";
@import "mixins";
 
*, *:after, *:before {
    margin: 0;
    padding: 0;
    @include border-box;
    }
 
img {
    width: auto;
    max-width: 100%;
    height: auto !important;
    }
 
.wrapper {
    width: 100%;
    margin: 0 auto;
    }
 
.wrapper, .row {
    @extend %clearfix;
    }
 
[class*='column-'] {
    float: left;
    padding: 1em;
    width: 100%;
    min-height: 1px;
    }
 
@media #{$breakpoint-medium} {
    .wrapper {
        width: 95%;
        max-width: $grid-max-width;
        }
    @for $i from 1 through $grid-columns {
        .column-#{$i} {
            width: 100% / $grid-columns * $i;
            }
        }
    }