Congrats on the launch Imbue team!
I used Sculptor to build most of https://lingolog.app/ (featured in this post).
It was a blast - I was cooking dinner and blasting out features, coming back to see what Sculptor had cooked up for me in the meantime. I also painted the landing page in procreate while Sculptor was whirring away.
Of course, this meant that my time shifted from producing code to reviewing code. I found the diffs, Sculptor's internal to-do list, and summaries all helpful to this end.
n.b. I'm not affiliated with the team, but I've worked with some Imbue team members many years ago which led to being a beta tester.
Not a duolingo alternative, but I recently built a (WIP) web app for journaling in your target language with LLM-powered feedback and in-context word discovery.
I built it for myself as I wanted to practice writing in my target languages, while also wanting to learn new words... The idea was that hopefully I would remember the words if I could associate them to my journal for that day.
It's a little clunky, but give it a go if you're interested!
Right now it's a bring-your-own claude token model, but let me know if you're not comfortable with that.