_styles.scss

// _styles.scss

// all styles not in media queries are served through "my-base"
@include my-base {
  header, section, aside, footer {
    background-color: #ddd;
    margin: 1em 5%;
    padding: 1em 5%;
    width: 80%;
    float: left;
  }
}

// all media query styles are served through "my-media"
@include my-media("(min-width: 40em)") {
  section, aside {
    width: 30%;
  }
  aside {
    float: right;
  }
}

// the "false" parameter hides these styles from old IE
@include my-media("(min-width: 60em)", false) {
  section {
    width: 45%;
  }
  aside {
    width: 15%;
  }
  aside {
    float: right;
  }
}