use mixin to store media query code example

Example: media query mixin

@mixin for-phone-only {  @media (max-width: 599px) { @content; }}
@mixin for-tablet-portrait-up {  @media (min-width: 600px) { @content; }}
@mixin for-tablet-landscape-up {  @media (min-width: 900px) { @content; }}
@mixin for-desktop-up {  @media (min-width: 1200px) { @content; }}
@mixin for-big-desktop-up {  @media (min-width: 1800px) { @content; }}