Couple suggestions after playing with this:

1) the experience mostly works on mobile (where I first tried it). With only minimal changes in the fixed sizing I think you could make this mobile friendly.

2) for posts shared via your Twitter, would be interesting to see details about the prompt(s) used vs “new post”

3) I’d like to have a bit more customization in the options

Overall really nice and good luck with monetizing it. I’d love to see a blog post write up on the technical implementation. That’s something I’d more be willing to pay to see personally.