I’m open sourcing the IF-authoring language behind Storealis.
You can try it out now at https://narrators.club (no accounts, all online & cloud-backed).
Find the authoring guide here https://biarity.gitlab.io/page/narratorsclub.
It’s very clean, easy to use, and very flexible - mainly for making advanced choice-based games. It has an online IDE and interpreter/reader so it works everywhere! Of course it’s free, and soon open source too.