Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.14)
// Compass (v1.0.1)
// ----

// make a mixin for the border radius and anything else you can see that might be needed. 

@mixin box-sizing($box: border-box) {
  -webkit-box-sizing: $box;
     -moz-box-sizing: $box;
          box-sizing: $box;   
}

@mixin shape($height: null, $width: null) {
  height: $height;
  width: $width;
}

*,
*:before,
*:after {
  @include box-sizing;
}

.module {
  background-color: #CCFF99;
  display: block;
  @include box-sizing(8px);
  @include shape(300px, 400px);
  margin-left: auto;
  margin-right: auto;
  padding: 1em 5%;
}
.module h3 {
  background: #FFFFFF;
  @include box-sizing(4px);
  font-size: 2.4em;
  line-height: 1.4;
  vertical-align: middle;
  @include shape(null, 100%); // won't output height
}

.btn {
  background-color: #FFFFFF;
  color: #CCFF99;
  display: block;
  font-size: 1.2em;
  line-height: 1.4;
  margin-left: auto;
  margin-right: auto;
  vertical-align: middle;
  
}

SassMeister-output.css

*,
*:before,
*:after {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

.module {
  background-color: #CCFF99;
  display: block;
  -webkit-box-sizing: 8px;
  -moz-box-sizing: 8px;
  box-sizing: 8px;
  height: 300px;
  width: 400px;
  margin-left: auto;
  margin-right: auto;
  padding: 1em 5%;
}

.module h3 {
  background: #FFFFFF;
  -webkit-box-sizing: 4px;
  -moz-box-sizing: 4px;
  box-sizing: 4px;
  font-size: 2.4em;
  line-height: 1.4;
  vertical-align: middle;
  width: 100%;
}

.btn {
  background-color: #FFFFFF;
  color: #CCFF99;
  display: block;
  font-size: 1.2em;
  line-height: 1.4;
  margin-left: auto;
  margin-right: auto;
  vertical-align: middle;
}