We apologize for the instability of composr.app and appreciate your patience. We are working on the statistics addon and trying to find an optimal way to store and render data. Unfortunately, we have yet to find a solution that can handle the traffic (and therefore, tens of millions of statistical records) of composr.app. We're working hard on one.
I don't know if I like it personally. For me, the non-nested version is more readable and understandable because then I don't have to keep scrolling up to see which classes / selectors apply to what. I'd definitely like to also implement to/from compiler tools along with this.
https://caniuse.com/?search=css%20nesting