how to create mixins in scss code example

Example 1: sass mixin

@mixin transform($property) {
  -webkit-transform: $property;
  -ms-transform: $property;
  transform: $property;
}
.box { @include transform(rotate(30deg)); }

Example 2: scss variables mixins

// _base.scss
$font-stack:    Helvetica, sans-serif;
$primary-color: #333;

body {
  font: 100% $font-stack;
  color: $primary-color;
}

Example 3: sass mixin

@mixin css-triangle($color, $direction, $size: 6px, $position: absolute, $round: false){
    @include pseudo($pos: $position);
    width: 0;
    height: 0;
    @if $round {
        border-radius: 3px;
    }
    @if $direction == down {
        border-left: $size solid transparent;
        border-right: $size solid transparent;
        border-top: $size solid $color;
        margin-top: 0 - round( $size / 2.5 );
    } @else if $direction == up {
        border-left: $size solid transparent;
        border-right: $size solid transparent;
        border-bottom: $size solid $color;
        margin-bottom: 0 - round( $size / 2.5 );
    } @else if $direction == right {
        border-top: $size solid transparent;
        border-bottom: $size solid transparent;
        border-left: $size solid $color;
        margin-right: -$size;
    } @else if  $direction == left {
        border-top: $size solid transparent;
        border-bottom: $size solid transparent;
        border-right: $size solid $color;
        margin-left: -$size;
    }
}