This is version of CTUstyle (see http://petr.olsak.net/ctustyle-e.html) for usage in OpTeX. It is derived from CTUstyle2 (new design).
This package can serve as an example of OpTeX’s macro package.
See ctustyle-doc.pdf for information of how to use CTUstyle (sorry, this is in Czech language only, only abstract is in English).
You can see TUGboat article too https://www.tug.org/TUGboat/tb36-2/tb113olsak.pdf
For using \slides with CTUstyle design, see slides.pdf file.