> My site uses CSS to respect light/dark theme, so has no manual toggle. It requires Javascript and I have a personal goal to have a JS-free site, just pure HTML and CSS. I also think that a site should respect the user's own light/dark settings, and so a toggle, if one ever exists for a site, should really be a browser setting on the browser toolbar.

I agree that it should definitely respect the OS level setting but I really like it when I'm given the option to override that setting. What if I don't like the way a site implemented their dark mode styles and I would rather switch back to light mode for just that one site. Having no toggle on the site I would have to go to my OS level settings, turn dark mode off, then later remember to go back to my OS level settings and turn it back on.

That's very flattering. So I'll relay some comments on your site:

- you make sentence-spacing a major design goal. I looked into that a bit ago and I found little or no real evidence that sentence-spacing is a good idea (https://gwern.net/doc/design/typography/sentence-spacing/ind...) and it would be expensive to implement: you do the only reasonable thing of injecting <span>s... but oh so many <span>s. If you get long pages like mine, that is going to cost you - DOM nodes are not free, soldier! - one issue with sentence-spacing is that you are fighting HTML & CSS the entire way. They just do not want to do it. You correctly note that it's hard, but you accidentally demonstrate it's even harder than you thought: you have justification enabled but not hyphenation... so all that happens is that sentences get stretched out to make them fully-justified and you get large double-spaces everywhere! Your current implementation winds up being not so much 'sentence-spacing' as 'every few words spacing'. (This is especially glaring in the sidenotes, like on the page I'm looking at right now, 'Stephen Zamadics' looks like 'Stephen_________Zamadics'. Since you set the column narrow, you probably want good hyphenation too... perhaps server-side, if you're deadset against JS.) - Dropcap positioning is hard, especially if you'd like it to work on more than one browser, and I'm not surprised yours has problems; pretty much everyone screws those up. (At least, I assume you don't intend the positioning problems like the '1' almost overlapping the 'someone' in cases like https://daveon.design/creating-joy-in-the-user-experience.ht... .) - I think the dotted underlining is too hard to see: much too small and close to the link. Are you sure you don't need `text-decoration-thickness: from-font` & `text-underline-position: from-font`? - Rubricating the entire sidenote on hover seems excessive. - Sidenote numbering is very confusing. They get numbered 1/2/3/4... and then all lose their numbers in favor of ''? Mixing numbered & unnumbered is confusing enough, but then transitioning at the utterly arbitrary '5' let me baffled and wondering if the ''s were supposed to be a separate kind of sidenote like a margin-note. Definitely a case for 0/1/infinity. - Sidenotes come off as cluttered and hard-to-read, at least partially because they are all 1 big paragraph. Breaking them up would increase readability. I hope you didn't inherit Tufte-CSS's unnecessary and artificial limitation to non-block elements...? (I can't believe they refuse to fix that.) - EB Garamond is a variable font, which is a bit of a questionable choice because OS+browser support is still relatively low. (Just browser-wise, it's only at ~95% global https://caniuse.com/?search=variable%20font so add on OS incompatibility... The text should still render, but it won't look like you expect it to. Example: https://share.obormot.net/screenshots/Arcturus_Screen%20Shot... Also shows the sentence-spacing problems & dropcap problems.) - The use of auto-smallcaps (after H1s, I guess?) winds up feeling busy and confusing. Look at a page like https://daveon.design/about-dave-on-design.html where the sections so short - it winds up feeling like smallcaps is just being sprayed around at random, and the logic is lost. - Your image dragging widget is mysterious. The icons are unfamiliar and so small that they signal non-interactive. - am I imagining it or are your <hr>-asterisk-thingies weirdly offset to the right? - The lack of any header or obvious site navigational apparatus, despite the very large header, makes the site feel somehow cramped and confining. You must like your tree - have you considered the classic HTML approach of an image map? - The use of triangles in the ToC is a bad idea. They look too much like collapse/disclosures, which are becoming increasingly common, especially in ToCs like this, especially when the reader has already seen you use black-dots for unordered list markers. - Easter eggs like `X-Clacks-Overhead` are fine, but the page should still validate... (Doesn't look like a legal http-equiv to me: https://html.spec.whatwg.org/multipage/semantics.html#attr-m... ) - You have low-hanging fruit in performance and can definitely render faster: https://pagespeed.web.dev/analysis/https-daveon-design-about... - Tooltips, tooltips, tooltips!