Bootstrap 3 Style Grid built on Bourbon Neat in SCSS (2015)

_grid.scss

// Main containers
.container {
  @include outer-container();
}

// Rows
.row {
  @include row();
  padding-right: 15px;
  padding-left: 15px;
}


// A basic column without a defined width or height
.col {
  float: left;
  display:inline-block;
}

// Common styles for small and large grid columns
.col-xs-1,
.col-xs-2,
.col-xs-3,
.col-xs-4,
.col-xs-5,
.col-xs-6,
.col-xs-7,
.col-xs-8,
.col-xs-9,
.col-xs-10,
.col-xs-11,
.col-xs-12,
.col-sm-1,
.col-sm-2,
.col-sm-3,
.col-sm-4,
.col-sm-5,
.col-sm-6,
.col-sm-7,
.col-sm-8,
.col-sm-9,
.col-sm-10,
.col-sm-11,
.col-sm-12,
.col-md-1,
.col-md-2,
.col-md-3,
.col-md-4,
.col-md-5,
.col-md-6,
.col-md-7,
.col-md-8,
.col-md-9,
.col-md-10,
.col-md-11,
.col-md-12,
.col-lg-1,
.col-lg-2,
.col-lg-3,
.col-lg-4,
.col-lg-5,
.col-lg-6,
.col-lg-7,
.col-lg-8,
.col-lg-9,
.col-lg-10,
.col-lg-11,
.col-lg-12 {
  position: relative;
  // Prevent columns from collapsing when empty
  min-height: 1px;
}
// Create the Extra small grid
@include grid-core(xs);

// Create the small grid
@include media(min-width $screen-sm) {
  .container {
	max-width: $screen-sm;
	@include grid-core(sm);
  }
}

// Create the medium grid
@include media(min-width $screen-md) {
  .container {
	max-width: $screen-md;
	@include grid-core(md);
  }
}

// Create the large grid
@include media(min-width $screen-lg) {
  .container {
	@include outer-container;
	@include grid-core(lg);
  }
}

// centered columns styles
.row-centered {
  text-align:center !important;
}
.col-centered {
  display:inline-block !important;
  float:none !important;
  /* reset the text-align */
  text-align:left;
  /* inline-block space fix */
  // margin-right:-4px;
}

_mixins.scss

// Grid Mixins

// Create the grid for a given size
// This will loop over the number of columns and create a css class
// for each. If it's the last gride size, then let's not add a float
@mixin grid-core($size) {
  @for $i from 1 through $grid-columns {
	.col-#{$size}-#{$i} {
	  // Ignore float for the largest grid size
	  @if $i < $grid-columns {
		float: left;
		@include span-columns($i);
	  }
	}
	// If it's not the screen-xs, then let's add push and pull helper classes
	@if $size != "xs" {
	  .col-#{$size}-push-#{$i} {
		left: flex-grid($i, $grid-columns) + flex-gutter($grid-columns);
	  }
	  .col-#{$size}-pull-#{$i} {
		right: flex-grid($i, $grid-columns) + flex-gutter($grid-columns);
	  }
	}
  }
}

_variables.scss

//Neat Grid System

//phone:
$phone: 480px;

//tablet:
$tablet: 720px;

//desktop:
$desktop: 982px;

//tv:
$tv: 1278px;


$grid-columns: 12 !default;
$max-width: $tv;
$border-box-sizing: true !default;
// Padding, to be divided by two and applied to the left and right of all columns
$modular-scale-ratio: $golden;
$modular-scale-base: 1.2em;
$gutter: modular-scale(1, 1);



//== Media queries breakpoints
//
//## Define the breakpoints at which your layout will change, adapting to different screen sizes.

// Extra small screen / phone
//** Deprecated `$screen-xs` as of v3.0.1
$screen-xs:                  $phone !default;
//** Deprecated `$screen-xs-min` as of v3.2.0
$screen-xs-min:              $screen-xs !default;
//** Deprecated `$screen-phone` as of v3.0.1
$screen-phone:               $screen-xs-min !default;

// Small screen / tablet
//** Deprecated `$screen-sm` as of v3.0.1
$screen-sm:                  $tablet !default;
$screen-sm-min:              $screen-sm !default;
//** Deprecated `$screen-tablet` as of v3.0.1
$screen-tablet:              $screen-sm-min !default;

// Medium screen / desktop
//** Deprecated `$screen-md` as of v3.0.1
$screen-md:                  $desktop !default;
$screen-md-min:              $screen-md !default;
//** Deprecated `$screen-desktop` as of v3.0.1
$screen-desktop:             $screen-md-min !default;

// Large screen / wide desktop
//** Deprecated `$screen-lg` as of v3.0.1
$screen-lg:                  $tv !default;
$screen-lg-min:              $screen-lg !default;
//** Deprecated `$screen-lg-desktop` as of v3.0.1
$screen-lg-desktop:          $screen-lg-min !default;

// So media queries don't overlap when required, provide a maximum
$screen-xs-max:              ($screen-sm-min - 1) !default;
$screen-sm-max:              ($screen-md-min - 1) !default;
$screen-md-max:              ($screen-lg-min - 1) !default;


//== Grid system
//
//## Define your custom responsive grid.

//** Number of columns in the grid.
$grid-columns:              12 !default;
//** Padding between columns. Gets divided in half for the left and right.
$grid-gutter-width:         30px !default;
// Navbar collapse
//** Point at which the navbar becomes uncollapsed.
$grid-float-breakpoint:     $screen-sm-min !default;
//** Point at which the navbar begins collapsing.
$grid-float-breakpoint-max: ($grid-float-breakpoint - 1) !default;


//== Container sizes
//
//## Define the maximum width of `.container` for different screen sizes.

// Small screen / tablet
$container-tablet:             ($tablet + $grid-gutter-width) !default;
//** For `$screen-sm-min` and up.
$container-sm:                 $container-tablet !default;

// Medium screen / desktop
$container-desktop:            ($desktop + $grid-gutter-width) !default;
//** For `$screen-md-min` and up.
$container-md:                 $container-desktop !default;

// Large screen / wide desktop
$container-large-desktop:      ($tv + $grid-gutter-width) !default;
//** For `$screen-lg-min` and up.
$container-lg:                 $container-large-desktop !default;