From publisher blurb:
Cast a Little Spell On Me
So You’re a Teenage Witch is a freeform, build-your-own spells witchcraft system that is designed to be used with the vs. M Engine, especially in vs. Stranger Stuff — Season 2 (with added Easy and Hard Mode rules, even). Designed as an add-on to the game anyone can enjoy, options are included for how your Gamemaster wants to introduce witchcraft, with it all ideally balanced enough to have “being a witch” not need to even be a Good Gimmick (though those options are presented as well).
All you need to get started is a standard vs. Stranger Stuff — Season 2 character (and that core ruleboook of course) and these rules and you can seamlessly integrate your characters becoming budding witches in no time!