As of late I have been busy working on tools to bring the traditional UNIX text processing tools to the Web.

Currently there are two compilers, one that takes eqn code and generate LaTeX code, which then gets rendered by (for example) KaTeX, and a second one that takes tbl code, and generates a HTML table. Both are still on a very early phase, though you can already write fairly complex equations with the eqn compiler.

You can get a feeling of what is like to write mathematical equations with eqn at eqnonline.