site/_sass/_mixins.scss

@mixin box-shadow($shadow...) {
  -webkit-box-shadow: $shadow;
     -moz-box-shadow: $shadow;
          box-shadow: $shadow;
}

@mixin border-radius($radius...) {
  -webkit-border-radius: $radius;
     -moz-border-radius: $radius;
          border-radius: $radius;
}

@mixin border-top-left-radius($radius...) {
  -webkit-border-top-left-radius: $radius;
     -moz-border-radius-topleft:  $radius;
          border-top-left-radius: $radius;
}

@mixin border-top-right-radius($radius...) {
  -webkit-border-top-right-radius: $radius;
     -moz-border-radius-topright:  $radius;
          border-top-right-radius: $radius;
}

@mixin transition($transition...) {
  -webkit-transition: $transition;
     -moz-transition: $transition;
       -o-transition: $transition;
          transition: $transition;
}

@mixin user-select($select...) {
  -webkit-user-select: $select;    /* Chrome all / Safari all */
     -moz-user-select: $select;    /* Firefox all */
      -ms-user-select: $select;    /* IE 10+ */
       -o-user-select: $select;
          user-select: $select;
}