The idea is pretty cool, but I'm unsure of the mix of TUI and animation. Once you start going down the path of animations, layout, fonts, etc, you start just reinventing the web - but with extra steps.
Personally I would cut complex animations (i.e. sub-character) and only have a single size monospace font. I would rip out CSS and go for maximum compatibility. (If something exists like that, please let me know!)
Another feature that could be cool is to have this served (optionally) via telnet. I would also make it be able to produce static content (with a subset of features).
Tbh this can all be covered by ANSI escape codes. They aren't very expressive or compasable, in comparison to CSS but adequate for most TUI programms. And even the DX around them is okay-ish in textual and other TUI frameworks.
I like the telnet idea. I haven't used that in like 20 years. Do people still use that?
I guess it's kinda like running over ssh? Or do you mean you hit an open unprotected port (telnet) and then the app takes care of setting up the SSL connection so you don't have to worry about SSH details?
Personally I would cut complex animations (i.e. sub-character) and only have a single size monospace font. I would rip out CSS and go for maximum compatibility. (If something exists like that, please let me know!)
Another feature that could be cool is to have this served (optionally) via telnet. I would also make it be able to produce static content (with a subset of features).