Hey, thanks for your time!
You are right, there is no close button. I had in mind the idea to export to web to embed it - this is what I didn't think of having a close button, but in the release day I saw pretty important differences in the way it was displayed in itchio, so I had to fallback to native windows. And, of course, didn't think of that. New learning for the next time: take time for the itchio size, or add an esc button :)