Susy grids default configuration - inside gutters

_grid.scss

$column-count: 12;

$susy: (
  	columns: $column-count,
  	global-box-sizing: border-box,
  	gutter-position: inside,
	// debug: ( // Optional debug option to show grid on front-end
	//     image: show-columns,
	//     output: overlay,
	//     toggle: bottom left
	// )
);

.container {
	@include container($column-count);
	max-width: $breakpoint-full; // Max width. eg: 1140px
	position: relative;
	z-index: 2;
	@media (max-width: $breakpoint-full + 40px) {
		padding: 0 20px;
	}
}

$i: 1;
// Column classes
@for $i from 1 through $column-count {
  %col-#{$i},
  .col-#{$i} {
    @include span($i);
    @media (max-width: $breakpoint-medium) { // Mobile breakpoint - eg: 720px
    	width: 100% !important; // Using !important to ensure width is overridden
    }
  }
}