sassでmediaQuery

$breakpoints: ('sm': 'screen and (max-width: 400px)','md': 'screen and (max-width: 700px)','lg': 'screen and (max-width: 1200px)'  ) !default

@mixin mq($breakpoint: md)
  @media #{map-get($breakpoints, $breakpoint)}
    @content

.myBr
    display: inline

    @include mq(lg)
        display: inline
    @include mq(md)
        display: none
    @include mq(sm)
        display: none