A basic SASS mixin that makes OpenType features easier to work with on the web.

_opentype-features.scss

@mixin openTypeFeatures(
  $discretionary, 
  $historical, 
  $proportional-nums,
  $tabular-nums, 
  $oldstyle-nums, 
  $lining-nums, 
  $superscript, 
  $subscript, 
  $scientific-inferiours, 
  $ordinals,
  $slashed-zero, 
  $fractions,
  $caps-to-sc,
  $lowercase-to-sc,
  $caps-to-pc,
  $lowercase-to-pc,
  $uppercase-varients,
  $uppercase-spacing,
  $swashes,
  $contextual-swashes,
  $historical-forms,
  $titling-alternates
  ){  

  $standard-syntax: "dlig" $discretionary, "hlig" $historical, "pnum" $proportional-nums, "tnum" $tabular-nums, "onum" $oldstyle-nums, "lnum" $lining-nums, "sups" $superscript, "subs" $subscript, "sinf" $scientific-inferiours, "ordn" $ordinals, "zero" $slashed-zero, "frac" $fractions, "c2sc" $caps-to-sc, "smcp" $lowercase-to-sc, "c2pc" $caps-to-pc, "pcap" $lowercase-to-pc, "case" $uppercase-varients, "cpsp" $uppercase-spacing, "swsh" $swashes, "cswh" $contextual-swashes, "hist" $historical-forms, "titl" $titling-alternates;

  $legacy-syntax: 'dlig='+$discretionary+', hlig='+$historical+', pnum='+$proportional-nums+', tnum='+$tabular-nums+', onum='+$oldstyle-nums+', lnum='+$lining-nums+', sups='+$superscript+', subs='+$subscript+', sinf='+$scientific-inferiours+', ordn='+$ordinals+', zero='+$slashed-zero+', frac='+$fractions+', c2sc='+$caps-to-sc+', smcp='+$lowercase-to-sc+', c2pc='+$caps-to-pc+', pcap='+$lowercase-to-pc+', case='+$uppercase-varients+', cpsp='+$uppercase-spacing+', swsh='+$swashes+', cswh='+$contextual-swashes+', hist='+$historical-forms+', titl='+$titling-alternates;      

  -moz-font-feature-settings: $standard-syntax;
  -moz-font-feature-settings: $legacy-syntax;
  -ms-font-feature-settings: $standard-syntax;
  -o-font-feature-settings: $standard-syntax;
  -webkit-font-feature-settings: $standard-syntax;
  font-feature-settings: $standard-syntax; 
}