Simple Fluid Grid with responsive font sizing

base.css.scss

// Responsive text sizing
html {
  @media (min-width: 768px) {
    font-size: 62.5%;
  }
  @media (max-width: 767px) {
    font-size: 52.5%;
  }
  @media (max-width: 504px) {
    font-size: 42.5%;
  }
}

body {
  text-shadow: none;
  font-style: normal;
  text-transform: normal;
  font-size: 1.4rem;
  line-height: 1.625;
  font-weight: 400;
  color: #222;
  -webkit-font-smoothing: subpixel-antialiased;
}

h1, h2, h3, h4 {
  margin-top: 0;
  font-weight: 300; }
h1 { font-size: 4.0rem; line-height: 1.2;  }
h2 { font-size: 3.6rem; line-height: 1.25; }
h3 { font-size: 3.0rem; line-height: 1.3;  }
h4 { font-size: 2.4rem; line-height: 1.35; }
h5 { font-size: 1.8rem; line-height: 1.5;  }
h6 { font-size: 1.5rem; line-height: 1.6;  }

.row {
  display: block;
  @include box-sizing(border-box);
  .col {
    display: block;
    float: left;
    max-width: 100%;
    @include box-sizing(border-box);
  }
  // -- Col Sizes
  .col-1 {
    width: 8.333333333%;
  }
  .col-2 {
    width: 16.666666667%;
  }
  .col-3 {
    width: 25%;
  }
  .col-4 {
    width: 33.3333333333%;
  }
  .col-5 {
    width: 41.6666666666%;
  }
  .col-6 {
    width: 49.7777777778%;
  }
  .col-7 {
    width: 58.333333333%;
  }
  .col-8 {
    width: 66.666666667%;
  }
  .col-9 {
    width: 75%;
  }
  .col-10 {
    width: 83.333333333%;
  }
  .col-11 {
    width: 91.666666667%;
  }
  .col-12 {
    width: 100%;
  }
  // -- Auto clearfix .row
  &:before,
  &:after {
      content: " ";
      display: table;
  }
  &:after {
      clear: both;
  }
  // -- Center row
  &.row-center > .col {
    float: none;
    margin: 0 auto;
    min-width: 560px;
  }
}

// MOZILLLA PERCENT ROUNDING GRID FIX
@-moz-document url-prefix() {
  .row {
    .col-5 {
      width: 41.11111112%;
    }
    @media (max-width: 502px) {
      .col-5 {
        width: 40%;
      }
    }
  }
}

// Vertical align cols
.row.v-align {
  display: table;
  width: 100%;
  .col {
    display: inline-block;
    vertical-align: middle;
    float: none;
  }
}

// Grid Responsive

@media (max-width: 768px) {
  .row .col.col-xl,
  .row.row-xl .col {
    float: none;
    width: auto;
  }
  .row .col-x6 {
    width: 49.7777777778%;
  }
  .row.row-center > .col {
    min-width: 0;
  }
}