media queries scss

                                        // respond is the name of your mixin

    @mixin respond ($breakpoint) {

        // $breakpoint is simply a variable that can have several values

        @if $breakpoint==tablet {

            // here `laptop` is the value of $breakpoint
            // when call laptop, we mean the following piece of code        

        @media only screen and (max-width: 600px) {
          @content;
        }
      }

      @if $breakpoint==mobile {
        @media only screen and (max-width: 480px) {
          @content;
        }
      }
    }

                                    @mixin breakpoint($size) {
    @if $size == mobile {
      @media (max-width: 599px) { @content; }
    } @else if $size == tablet-portrait-up {
      @media (min-width: 600px) { @content; }
    } @else if $size == tablet-landscape-up {
      @media (min-width: 768px) { @content; }
    } @else if $size == laptop-desktop {
      @media (min-width: 992px) { @content; }
    } @else if $size == extra-large-devices {
      @media (min-width: 1200px) { @content; }
    }
}

.header{
    height: 10vh;
    display: flex;
    justify-content: space-between;
    border-bottom: 2px solid black;
}

                                    
  @media #{$small-and-down} {
    // styles for small screens and down
  }
  @media #{$medium-and-up} {
    // styles for medium screens and larger
  }
  @media #{$medium-and-down} {
    // styles for medium screens and down
  }
  @media #{$large-and-up} {
    // styles for large screens and up
  }
  @media #{$extra-large-and-up} {
    // styles for extra large screens and up
  }