Generated by SassMeister.com.

SassMeister-input-HTML.haml

%header
  %h1 Flexbox
  %p Comparison of different Flex values
%article
  %h2 flex: 100px
  %section.flex-container.hundredpx
    .box.flex1
      %h3 One
    .box.flex1
      %h3 Two
    .box.flex2
      %h3 Three
    .box.flex1
      %h3 Four
  %h2 flex: 0
  %section.flex-container.auto
    .box.flex1
      %h3 One
    .box.flex1
      %h3 Two
    .box.flex2
      %h3 Three
    .box.flex1
      %h3 Four
  %h2 flex: auto
  %section.flex-container.zero
    .box.flex1
      %h3 One
    .box.flex1
      %h3 Two
    .box.flex2
      %h3 Three
    .box.flex1
      %h3 Four
  %h2 flex: 1
  %section.flex-container.shorthand
    .box.flex1
      %h3 One
    .box.flex1
      %h3 Two
    .box.flex2
      %h3 Three
    .box.flex1
      %h3 Four

SassMeister-input.scss

// ----
// Sass (v3.3.0.rc.2)
// Compass (v1.0.0.alpha.17)
// ----

@import "compass";

$colors: (chartreuse, royalblue, plum, teal, lightsteelblue, sienna, maroon);

body {
  width: 80%;
  margin: 0 auto;
  padding: 2%;
  line-height: 1.6;
}

.flex-container {
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  margin: 1em 0;
  border: 1px solid #333;
}
.box {
  text-align: center;
}

@for $n from 1 through 4 {
  .box:nth-child(#{$n}) {
    background-color: nth($colors, $n);
  }
}

.flex1 {
  .hundredpx & {
    @include flex(1 1 100px);
  }
  .zero & {
    @include flex(1 1 0);
  }
  .auto & {
    @include flex(1 1 auto);
  }
  .shorthand & {
    @include flex(1);
  }
}
.flex2 {
  .hundredpx & {
    @include flex(2 1 100px);
  }
  .zero & {
    @include flex(2 1 0);
  }
  .auto & {
    @include flex(2 1 auto);
  }
  .shorthand & {
    @include flex(2);
  }
}

SassMeister-output.css

body {
  width: 80%;
  margin: 0 auto;
  padding: 2%;
  line-height: 1.6;
}

.flex-container {
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  margin: 1em 0;
  border: 1px solid #333;
}

.box {
  text-align: center;
}

.box:nth-child(1) {
  background-color: chartreuse;
}

.box:nth-child(2) {
  background-color: royalblue;
}

.box:nth-child(3) {
  background-color: plum;
}

.box:nth-child(4) {
  background-color: teal;
}

.hundredpx .flex1 {
  -webkit-flex: 1 1 100px;
  flex: 1 1 100px;
}
.zero .flex1 {
  -webkit-flex: 1 1 0;
  flex: 1 1 0;
}
.auto .flex1 {
  -webkit-flex: 1 1 auto;
  flex: 1 1 auto;
}
.shorthand .flex1 {
  -webkit-flex: 1;
  flex: 1;
}

.hundredpx .flex2 {
  -webkit-flex: 2 1 100px;
  flex: 2 1 100px;
}
.zero .flex2 {
  -webkit-flex: 2 1 0;
  flex: 2 1 0;
}
.auto .flex2 {
  -webkit-flex: 2 1 auto;
  flex: 2 1 auto;
}
.shorthand .flex2 {
  -webkit-flex: 2;
  flex: 2;
}

SassMeister-rendered.html

<header>
  <h1>Flexbox</h1>
  <p>Comparison of different Flex values</p>
</header>
<article>
  <h2>flex: 100px</h2>
  <section class='flex-container hundredpx'>
    <div class='box flex1'>
      <h3>One</h3>
    </div>
    <div class='box flex1'>
      <h3>Two</h3>
    </div>
    <div class='box flex2'>
      <h3>Three</h3>
    </div>
    <div class='box flex1'>
      <h3>Four</h3>
    </div>
  </section>
  <h2>flex: 0</h2>
  <section class='flex-container auto'>
    <div class='box flex1'>
      <h3>One</h3>
    </div>
    <div class='box flex1'>
      <h3>Two</h3>
    </div>
    <div class='box flex2'>
      <h3>Three</h3>
    </div>
    <div class='box flex1'>
      <h3>Four</h3>
    </div>
  </section>
  <h2>flex: auto</h2>
  <section class='flex-container zero'>
    <div class='box flex1'>
      <h3>One</h3>
    </div>
    <div class='box flex1'>
      <h3>Two</h3>
    </div>
    <div class='box flex2'>
      <h3>Three</h3>
    </div>
    <div class='box flex1'>
      <h3>Four</h3>
    </div>
  </section>
  <h2>flex: 1</h2>
  <section class='flex-container shorthand'>
    <div class='box flex1'>
      <h3>One</h3>
    </div>
    <div class='box flex1'>
      <h3>Two</h3>
    </div>
    <div class='box flex2'>
      <h3>Three</h3>
    </div>
    <div class='box flex1'>
      <h3>Four</h3>
    </div>
  </section>
</article>