sim3x

//var gulp =  require('gulp-sass');
var sass =  require('gulp-sass');

pipe(
      sass()
      .on('error', sass.logError)
)

$GLOBAL_FONT_SIZE: 18px; // this should be with 'px'

@mixin my-font ($font_size, $lineheight_size, $font){
  font: #{ $font_size * $GLOBAL_FONT_SIZE }/#{ $lineheight_size * $GLOBAL_FONT_SIZE } $font;
  font: #{ $font_size }rem/#{ $lineheight_size }rem $font;
}

.somestyle {
    @include my-font(1, 1.5, 'Arial sans-serif');
}

.somestyle {
  font: 18px/27px "Arial sans-serif";
  font: 1rem/1.5rem "Arial sans-serif";
}