https://ifdb.org/viewgame?id=z3scyumvgsr75blm

You've practiced long and hard for PotionComp, but Grusilda won't give up her title so easily. UGH! Curse that Grusilda!

You're just a poor young witch, surely innocent of any wrongdoing or malice, and yet you have attracted the attention of obnoxious Mean Girl witch Grusilda. She's arranged to divert you from the all-important potions competition to a lonely and cursed cabin in the middle of nowhere. Are you going to stand for that?

Oppositely Opal is a classic one-room adventure where you're trapped inside a cabin where every spell you cast has the opposite of its intended result -- often in the most perverse way possible.

Play in browser or download gblorb file (the latter requires a Glulxe interpreter).