Excellent project! I like the playground.

A while ago I made https://presentador.dev/ which was the same concept, write MD and produce an HTML based presentation.

Eventually I figured that I don't want to open my editor every time I wanted to create a presentation, so I made https://presentador.app/. It's like Slides.com but more opinionated. It's still under development but usable to create a simple presentation and new features are coming soon!