SASS & Flexbox ftw

.grid {
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;

    .row {
        display: flex;
        flex-wrap: wrap;

        @for $i from 1 to $grid-columns + 1 {
            .col-#{$i} {
                @if $grid-gutter > 0 {
                    width: calc(#{percentage(1 / $grid-columns * $i)} - #{$grid-gutter});
                    padding-right: $grid-gutter;
                } @else {
                    width: percentage(1 / $grid-columns * $i);
                }

                &:last-of-type {
                    width: percentage(1 / $grid-columns * $i);
                    padding-right: 0;
                }

                @include breakpoint(small) {
                    width: 100%;
                }
            }
        }

        @include breakpoint(small) {
            display: block;
        }
    }

    @include breakpoint(small) {
        display: block;
    }
}