Moving away from Tailwind, and learning to structure my CSS

Tailwind's Preflight is well-regarded and a perfectly reasonable choice. A few key points:

• It's built on top of modern-normalize, which is itself the modern successor to the classic normalize.css. So you're standing on solid, widely-used foundations.
• It's less of a pure "normalizer" and more of an opinionated reset. It does the cross-browser smoothing (like modern-normalize) but also adds opinions: removing default margins, unstyling headings/lists, making images block-level, etc.

That second point matters for your goal. A pure normalizer (like modern-normalize alone) just irons out browser inconsistencies and keeps sensible defaults. Preflight goes further and strips defaults so you decide everything. As Julia found, you may have unconsciously absorbed some of those opinions (e.g. box-sizing: border-box on everything, removed heading margins).

So the question for you is really: do you want a plain normalizer (keeps browser defaults, less to override) or an opinionated reset (blank slate, you style everything)?

Since you're learning to structure CSS deliberately, what's your instinct — start from a blank-slate reset like Preflight, or a gentler normalizer that keeps more defaults?

Nice — that's step 1 (reset) done. A couple of observations worth noting as you work through it:

• Putting it inside @layer base is a smart move. It means everything in your reset has the lowest priority, so any component CSS you write later will win over it without you needing to fuss about specificity. That matches Julia's interest in @layer as a structuring tool.
• This is the full ~200-line Preflight you described copying — it includes both the modern-normalize parts and Tailwind's opinionated bits (the margin: 0 on headings/p, the unstyled ol/ul, block-level images, border-width: 0 on everything).

That last point is the one to keep in mind: with border-width: 0 on every element, a plain border: 1px solid won't show up unless you also set a color — and you've lost default heading sizes and list bullets. That's intentional (blank slate), but it means you'll be adding those back deliberately as you build components.

Want to do a quick sanity check that the reset is actually taking effect before moving on to the next system (components)? Or would you rather press straight ahead?

Here's a small one — define two named layers, declare their order, then put a rule in each:

@layer theme, widgets;

@layer theme {
  p { color: rebeccapurple; }
}

@layer widgets {
  p { color: teal; }
}

The key idea: the @layer theme, widgets; line at the top sets the priority order (later = wins). So even though theme and widgets both target p, the text comes out teal — widgets is declared last, so it beats theme, regardless of source order or specificity.

Try dropping that into a <style> block with a <p> and see.

Let's start with the Badge — it's the simplest self-contained TAC component, and it's pure CSS (the JS evolution comes later). Here's a version you can drop into an %%html cell:

%%html
<style>
@layer components {
x-badge {
  display: none;
  min-width: 1.25rem;
  height: 1.25rem;
  border-radius: 0.625rem;
  place-content: center;
  background-color: blue;
  color: white;
}
x-badge[count]::before { content: attr(count); padding: 0 6px; }
x-badge[count]:not([count=""]):not([count="0"]) { display: inline-flex; }
}
</style>
<p>Cart <x-badge count="3"></x-badge></p>
<p>Empty <x-badge count="0"></x-badge></p>

The TAC ideas in play here:

• Tag: a custom x-badge tag (HTML has no badge element, so we invent one)
• Attribute: count carries the data and drives visibility — show only when count is present and non-zero
• No classes, no JS — just a tag styled by its attribute

I wrapped it in @layer components to match the structure you're building. Give it a run and see the badge appear only on the non-zero one.

The badge works! Here's what those pieces do:

place-content: center — shorthand for align-content + justify-content in one. On a flex/grid container it centres the content both ways. Here it's what centres the count number inside the badge circle (once display becomes inline-flex).

inline-flex — like flex (children laid out with flexbox), but the badge itself sits inline with surrounding text rather than breaking onto its own line. That's why the badge nestles next to "Cart" instead of dropping below it. This is also the value that reveals the badge — the base rule sets display: none, so the badge is hidden until a selector flips it to inline-flex.

The selectors:

• x-badge[count]::before — targets the ::before pseudo-element (generated content inserted before the tag's contents) of any x-badge that has a count attribute. content: attr(count) pulls the attribute's value in as text, so count="3" renders a "3".

• x-badge[count]:not([count=""]):not([count="0"]) — matches an x-badge that has count, and whose count is not empty string, and not "0". Each :not(...) excludes a case. So an empty or zero count stays display: none; anything else flips to inline-flex and becomes visible. That's the whole show/hide logic, done purely by attribute value.

The neat trick: the data (count="3") and the visibility rule live in the same attribute — no separate "hidden" class needed.

Sure! To understand these you need the idea of flexbox axes. A flex container lays its children out along two axes:

• Main axis — the direction items flow. For flex-direction: row (the default) that's horizontal (left→right). For column it's vertical.
• Cross axis — always perpendicular to the main axis. So for a row, the cross axis is vertical.

Each axis has a property that controls positioning along it:

• justify-content — positions content along the main axis. (Mnemonic: "justify" like justifying text left/right — it's the flow direction.)
• align-content — positions content along the cross axis.

So place-content: center (which expands to both set to center) means "centre along both axes" — horizontally and vertically centred.

Now, an important wrinkle. There are actually two families of alignment properties:

Here's the subtlety with the badge: align-content only does something visible when there are multiple lines (i.e. content has wrapped). With a single line of content, align-content: center often behaves the same as align-items: center in practice in modern browsers — so for the badge's single number, place-content: center ends up centring it nicely either way.

So the short version: place-content: center is a convenient one-liner that centres the badge's content both horizontally (justify-content) and vertically (align-content), which is exactly what you want for a small circular badge with a number in the middle.

Good choice, and you've correctly spotted the one real tradeoff. The reason TAC used x-badge rather than bare badge is the hyphen: a custom element name must contain a hyphen to be registrable via customElements.define(). A bare <badge> can never become a web component — the browser parses it as a generic unknown element (HTMLUnknownElement, styled inline by default). Since you're explicitly opting out of web components, that limitation costs you nothing.

The one thing worth keeping in the back of your mind is the same caveat the TAC article raised about adding striped to tables: a bare, un-prefixed tag could in principle collide with a future real HTML element if WHATWG ever ships a <badge>. The x- (or any hyphenated) prefix is insurance against that, since the spec guarantees hyphenated names are reserved for custom elements and will never be standardised. Low risk for a personal site, but that's the bet you're making.

For styling purposes the bare tag behaves identically — unknown elements accept CSS just fine, which is why your badge renders perfectly.

Exactly — and that's very much in the TAC spirit of "leverage what HTML gives you." If a native <badge> ever shipped, you'd likely get the baseline behaviour for free and just layer your own tweaks on top, the same way TAC treats <button ord="..."> or <table striped>: native element first, custom styling added only where needed.

There's even a nice safety net: if a future <badge> came with its own default display, your existing rules (display: none base + inline-flex when count is non-zero) would simply override it, so your show/hide logic keeps working regardless. You'd be enhancing the native element rather than fighting it.

So you're not really making a risky bet — you're writing CSS that degrades (or upgrades) gracefully either way.

A natural next step is the ordinal buttons — they show TAC's second idea: instead of inventing a tag, you add a custom attribute to a native HTML element. The article left the styles as ..., so let's fill them in with something real:

<style>
button[ord] {
  border: none; border-radius: 6px; padding: 6px 14px;
  font: inherit; cursor: pointer;
}
button[ord=primary] { background: royalblue; color: white; }
button[ord=secondary] { background: lightsteelblue; color: black; }
button[ord=tertiary] { background: transparent; color: royalblue; text-decoration: underline; }
</style>
<button ord="primary">Save</button>
<button ord="secondary">Cancel</button>
<button ord="tertiary">Learn more</button>

The key contrast with the badge: here we leverage the real <button> (so we keep all its built-in behaviour — focus, keyboard, form submission, accessibility) and only add an ord attribute to carry the variation. A bare <button> with no ord stays completely untouched.

Give it a run and we can tweak the look, or move on to another TAC pattern (striped table, dialog close-button, or the site-header relationships).

Right — the tertiary deliberately strips the background and reads almost like a plain link. That matches the article's point about ordinal ranking carrying meaning: primary shouts "do this", secondary is a quieter alternative, and tertiary recedes to a low-emphasis action that's barely more than text.

It's a nice illustration of why this is a variation (an attribute) rather than a separate component. All three are still the same native <button> — same behaviour, same accessibility — and the ord value just dials the visual emphasis up or down. The styling can range from "obviously a button" to "looks like a link" without ever changing what the element is.

A small thing you might play with: tertiary buttons often drop the padding too (so they align flush with surrounding text), but keeping it as-is gives a consistent hit-area across all three, which is friendlier for clicking. Either choice is defensible.

Let's try the striped table — it shows TAC's boolean attribute pattern (an attribute whose mere presence, with no value, switches on a style):

<style>
table[striped] tbody tr:nth-of-type(odd) { background-color: #f0f0f0; }
table[striped] th, table[striped] td { padding: 6px 12px; text-align: left; }
</style>
<table striped>
  <tbody>
    <tr><td>Apple</td><td>Red</td></tr>
    <tr><td>Banana</td><td>Yellow</td></tr>
    <tr><td>Grape</td><td>Purple</td></tr>
    <tr><td>Lemon</td><td>Yellow</td></tr>
  </tbody>
</table>

The key idea: table[striped] matches purely on the presence of the attribute — no =value needed, just like native booleans such as disabled or checked. A plain <table> stays unstyled; add the word striped and the zebra rows switch on.

The :nth-of-type(odd) is what does the alternating — it selects the 1st, 3rd, 5th... <tr> so only those get the grey background.

The remaining TAC idea we haven't touched is relationships — using parent/child selectors to compose elements. The <dialog> is a great one because it leverages a real native element that already handles focus-trapping, Escape-to-close, and the backdrop for you:

<style>
dialog button[slot=close] {
  position: absolute; top: 8px; right: 8px;
  border: none; background: none; font-size: 1.25rem; cursor: pointer;
}
dialog button[slot=close]::before { content: '×'; }
dialog { position: relative; border: none; border-radius: 8px; padding: 24px; }
</style>
<dialog open>
  <button slot="close" aria-label="Close dialog"></button>
  <div>Dialog content here...</div>
</dialog>

The TAC relationship: dialog button[slot=close] styles a button only when it's inside a dialog and carries slot=close. The button has meaning by virtue of its relationship to its parent — the same bare <button> elsewhere stays untouched.

I added open so it shows inline for now. The × comes from the ::before content, and position: absolute tucks it in the corner relative to the position: relative dialog.

You're right to question it. The slot attribute only has real functionality inside Shadow DOM — it assigns a node to a named <slot> in a component's shadow tree. Outside web components it does literally nothing functional. TAC is just using it as an arbitrary attribute to hang a CSS selector on — button[slot=close] is no more special than button[close] or button.close would be. So no, it gives you no CSS-specific benefit; it was just a naming choice to signal intent.

Since you're not using web components, I'd use a plain custom attribute instead, and wire the close up with hx-on:

<style>
dialog { position: relative; border: none; border-radius: 8px; padding: 24px; }
dialog button[close] {
  position: absolute; top: 8px; right: 8px;
  border: none; background: none; font-size: 1.25rem; cursor: pointer;
}
dialog button[close]::before { content: '×'; }
</style>
<dialog open>
  <button close aria-label="Close dialog" hx-on:click="this.closest('dialog').close()"></button>
  <div>Dialog content here...</div>
</dialog>

The relationship idea from TAC still holds — dialog button[close] only styles the button by virtue of its dialog parent — but now close is an honest custom attribute doing exactly one job (a CSS hook), and hx-on:click handles the behaviour inline without a separate script.

Using showModal() (rather than the open attribute) gives you automatic centering, a ::backdrop, and Escape-to-close for free:

<style>
dialog { border: none; border-radius: 12px; padding: 24px; min-width: 300px; box-shadow: 0 10px 40px rgba(0,0,0,0.2); }
dialog::backdrop { background: rgba(0,0,0,0.4); }
dialog { position: relative; }
dialog button[close] { position: absolute; top: 8px; right: 8px; border: none; background: none; font-size: 1.25rem; cursor: pointer; }
dialog button[close]::before { content: '×'; }
</style>
<button hx-on:click="document.getElementById('demo').showModal()">Open dialog</button>
<dialog id="demo">
  <button close aria-label="Close dialog" hx-on:click="this.closest('dialog').close()"></button>
  <h2>Hello!</h2>
  <div>This dialog is centered with a backdrop.</div>
</dialog>

showModal() is what makes it "dialog-ish" — the browser promotes it to the top layer, centers it in the viewport, and dims everything behind with ::backdrop. The close button still works via the same hx-on:click.

Good catch — that's almost certainly it. The Preflight reset is in @layer base, but layered author styles still sit in the author origin, which beats the UA origin where the browser's dialog:modal { margin: auto; inset: 0 } centering lives. So the reset's resets quietly knock out the native centering.

Easiest fix is to just assert the centering yourself in the (unlayered, so higher-priority) inline style:

<style>
dialog { inset: 0; margin: auto; border: none; border-radius: 12px; padding: 24px; min-width: 300px; box-shadow: 0 10px 40px rgba(0,0,0,0.2); }
dialog::backdrop { background: rgba(0,0,0,0.4); }
dialog button[close] { position: absolute; top: 8px; right: 8px; border: none; background: none; font-size: 1.25rem; cursor: pointer; }
dialog button[close]::before { content: '×'; }
</style>
<button ord="primary" hx-on:click="document.getElementById('demo').showModal()">Open dialog</button>
<dialog id="demo">
  <button close aria-label="Close dialog" hx-on:click="this.closest('dialog').close()"></button>
  <h2>Hello!</h2>
  <div>This dialog is centered with a backdrop.</div>
</dialog>

inset: 0 + margin: auto is exactly what the UA stylesheet does for modal dialogs — we're just restoring it explicitly so the reset can't win.

The one TAC example left from the article is the site header — it pushes the "relationships" idea further by enforcing a rigid nested structure (x-siteheader > header > nav > a) while still leaving the content open. It also gets to reuse your badge inside it:

<style>
x-siteheader { padding: 12px; background-color: lightgray; }
x-siteheader, x-siteheader > header { display: flex; align-items: center; }
x-siteheader::before { content: '🍔'; font-size: 2rem; margin-right: 12px; }
x-siteheader > header > nav > a { padding: 6px; }
x-siteheader > header > nav > a:hover { background-color: lightslategray; }
x-siteheader-extras { display: flex; align-items: center; gap: 12px; margin-left: auto; }
</style>
<x-siteheader>
  <header>
    <nav>
      <a href="home">Home</a>
      <a href="products">Products</a>
      <a href="support">Support</a>
    </nav>
  </header>
  <x-siteheader-extras>
    <a href="cart">Cart <badge count="1"></badge></a>
    <a href="account">Account</a>
  </x-siteheader-extras>
</x-siteheader>

This shows the deepest TAC pattern: the structure itself is part of the component contract. The descendant/child selectors (>) enforce that nav links live inside header > nav, the ::before bakes in a logo, and margin-left: auto on the extras pushes them to the right edge. Your badge from earlier slots right in.

You've put your finger on a real tension. The ::before logo is a common TAC-style trick, but it has a meaningful downside: pseudo-element content is presentational only. It's invisible to screen readers, can't be a link (a logo usually clicks through to home), can't have meaningful alt text, and isn't in the DOM for JS to grab. For a decorative flourish that's fine; for a logo — which is usually a real, clickable, named thing — it's a bit of a stretch.

So your instinct is the more idiomatic one for anything load-bearing:

<x-siteheader>
  <a href="home" class="logo"><img src="logo.png" alt="Acme Foods"></a>
  <header>…</header>
  …
</x-siteheader>

Rough rule of thumb: ::before/::after for decoration (icons, the badge's ×, separators, the attr(count) text), real elements for content (logos, anything clickable, anything that needs alt text or semantics).

The article leaned on ::before partly to make the point that the component can bake in its own logo with zero required markup — nice for a demo, but in practice a real <a><img></a> is the sturdier choice.

The simplest move is to broaden the selector so it matches any a inside the header — both the nav and the extras — instead of the deep > header > nav > path.

The margin-left: auto on x-siteheader-extras still pushes that group to the right, so you get identical link styling/hover on both sides with the positioning handled purely by the container. The tradeoff: x-siteheader a now matches all descendant links, so if you ever add a link you don't want styled this way, you'd need to be more specific again.

{
  "id": "toolu_01BSxnYLbEzKULfULQaXnZPx",
  "server": false,
  "call": {
    "function": "add_msg",
    "arguments": {
      "content": "def mk_siteheader(items:list, extras:list):\n    nav = Nav(*[A(t, href=h) for t,h in items])\n    return Siteheader(Header(nav), SiteheaderExtras(*[A(t, href=h) for t,h in extras]))",
      "msg_type": "code",
      "placement": "add_after"
    }
  },
  "result": "_57ba5013"
}

I've added a mk_siteheader function that builds the nav links from items and the extras from extras, each a list of (text, href) pairs. Give it a run and try it with something like mk_siteheader([('Home','home'),('Products','products')], [('Account','account')]).

Nice, that's more flexible. Here's how you'd call it:

mk_siteheader(
    [A('Home', href='home'), A('Products', href='products'), A('Support', href='support')],
    [A('Cart ', Badge(count=1), href='cart'), A('Account', href='account')])

The payoff of your design: the Cart link can carry a Badge inside it, which wouldn't be possible if mk_siteheader built the A tags from plain (text, href) pairs.

The FT components render exactly the structure your CSS expects — siteheader > header > nav > a for the links, and siteheader-extras holding the badge-bearing Cart link. Your mk_siteheader is now a clean reusable building block.

Yes — we've now worked through every example from the TAC article, covering all three of its core ideas:

• Tag (invent a new element): badge, siteheader
• Attribute (extend a native element): button[ord], table[striped]
• Relationship (compose via structure): dialog button[close], the siteheader > header > nav > a hierarchy

The only piece we skipped is the Badge's JavaScript evolution (the notification bell). The article did that with a web component, but since you're going the htmx route, that'd look quite different.

Yes — the word you're reaching for is tone (or emphasis/prominence), not lightness. The key insight in modern theming is that you want to name colours by their role relative to the background, not their absolute value. That way the same name works in both light and dark mode.

A few established vocabularies you could borrow from:

• Tonal / "tones" — Material Design 3 uses a tonal palette with numbers like 0–100 where the number is absolute lightness. But crucially, light mode picks tone 40 for a role while dark mode picks tone 80 for the same role. So the role name stays fixed; the tone number flips.

• Surface vs. on-surface — Material's role language: surface (background-ish) and on-surface (foreground that sits on it). This sidesteps light/dark entirely by naming the relationship.

• Subtle → bold / "steps" — Radix Colors uses a 12-step scale where step 1 is "app background" and step 12 is "high-contrast text". In their dark theme the same step numbers map to inverted lightness automatically. They describe steps by purpose (backgrounds, borders, text) rather than light/dark.

So rather than "lightest to darkest", the cleaner framing is something like "least prominent to most prominent" or "step 1 = closest to background, step 7 = closest to foreground". Then:

• Light mode: step 1 ≈ near-white, step 7 ≈ near-black
• Dark mode: step 1 ≈ near-black, step 7 ≈ near-white

The number means "how far from the background toward the foreground", which is exactly the inversion you described — and it reads identically in both themes.

For your fg/bg point: that maps neatly too. bg is "step 0" (the surface itself) and fg is "step ∞" (maximum contrast — true white/black if you want it), with your 7 steps as the graded territory in between.

So your col17 could instead be something like col17 meaning "palette 1, prominence 7" — the highest-contrast version of colour 1, whichever direction that is in the current theme.

Does that "prominence/step" framing fit what you had in mind?

For roles mapped to UI things, 7 distinct hues is actually a touch generous — most systems get by with fewer. The common set is roughly:

• primary — main brand actions (primary buttons, links)
• secondary — supporting accent
• neutral/gray — the workhorse for text, borders, surfaces (used far more than any hue)
• success — green-ish (confirmations)
• warning — amber-ish (caution)
• danger/error — red-ish (destructive actions)
• info — blue-ish (notices)

That's 7 if you count neutral, and it lines up almost exactly with your palette size. So 7 is very reasonable — it covers the standard semantic roles without sprawling.

One thing worth deciding early: is col1..col7 meant to be semantic (primary, danger, ...) or abstract (just 7 brand hues you map later)? Julia's file used literal hue names (--pink, --red). The role-based naming (--primary, --danger) tends to age better because the markup says intent not appearance — a primary button stays --primary even if you recolour the brand from blue to green.

You could even keep both layers: abstract hues at the bottom, semantic roles pointing at them:

:root {
  --col14: #3b6ea5;
  --primary: var(--col1-4);
}

That gives you the "all colours listed in one place" guarantee Julia wanted, plus a role layer that the components actually reference.

Makes sense. So the position carries a stable, loose semantic convention (col1 = neutral-ish, col3 = danger-ish, col5 = success-ish, ...) while the actual hue lives in the theme. A role layer maps onto positions (--danger: var(--col3?)), so swapping themes just means swapping which hues fill those slots — the role→position mapping stays put, and so does all your component CSS.

The nice consequence: a theme author only has to honour the convention ("slot 3 should read as alarming"), not match exact colours. A warm theme and a cool theme can pick totally different reds-or-oranges for col3 and both still work.

So the structure is three layers:

• hues by position (theme-specific): --col31 … --col37
• roles → positions (stable): --danger: var(--col36)
• components → roles: button[ord=danger] { background: var(--danger) }

One thing to pin down before we write it: when you say col3 "would work well for danger", is that a hard convention (every theme guarantees col3 is the alarming one) or just a typical tendency? That decides whether the role layer is shared across all themes or redefined per-theme.

Makes sense. So the convention is hard but lives in the theme, not the framework:

• Framework owns the stable role→position map: --danger: var(--col32). This never changes across themes.
• Theme author owns what col3-2 actually looks like, with a contract: "col3 is the danger slot, so make col3-2 read well as danger on a bright bg" — but they're free to honour that via vibrant red, grayscale, high-contrast, or colourblind-safe hues.
• Positions stay general-purpose: col3-2 is "the danger colour" by role, but nothing stops a component using it decoratively elsewhere. It's a colour that happens to be suitable for danger, not a colour that only means danger.

So the framework promises themes a fixed set of slots and tells authors what each slot will predominantly be used for; authors promise those slots work for their stated roles. The component CSS only ever references roles, so it's fully theme-agnostic.

That gives a clean separation: swap the theme → hues change; the role map and every component stay untouched.

Not quite just saturation/brightness — and that's the crux of why this is hard. The naive approach is "take the hue, then ramp HSL lightness from high to low" but that produces perceptually uneven steps: equal numeric jumps in HSL lightness don't look like equal jumps to the eye, and saturation drifts oddly (mid-tones look washed out, darks look muddy).

A few ways to scale "intensity", roughly worst→best:

• HSL lightness ramp — easy, but perceptually lumpy and hue shifts as you darken. Fine for a quick start.
• HSB/HSV with paired L+S curves — better; you usually lower lightness and raise saturation together toward the dark end so darks stay rich rather than greying out. This is what a lot of hand-tuned palettes (Tailwind's old scales) effectively do.
• A perceptual space — OKLCH — the modern best answer. You vary L (perceptual lightness) in roughly even steps and keep H (hue) fixed, adjusting C (chroma) along a curve. Because OKLCH lightness is perceptually uniform, equal L steps look equal, and hue stays put as you darken.

So your second number is best thought of as perceptual lightness (L), with chroma as a secondary curve riding along it — not a raw saturation+brightness blend.

For 7 steps, a clean OKLCH starting point:

--col31: oklch(0.97 0.03 25);
--col32: oklch(0.90 0.07 25);
--col33: oklch(0.80 0.12 25);
--col34: oklch(0.68 0.18 25);
--col35: oklch(0.55 0.20 25);
--col36: oklch(0.43 0.17 25);
--col37: oklch(0.30 0.12 25);

Notice the pattern: L marches down fairly evenly (0.97→0.30), H is fixed (25, a red), and C rises to a peak around the mid-vivid steps then eases off at the very light and very dark ends (pale tints and deep shades can't hold high chroma). That chroma "arch" is the trick that keeps both ends from looking muddy.

For the dark-mode inversion you wanted: keep the same L values mapped to the same step numbers, but flip which end the role layer reaches for — or simply redefine the steps with L ascending. Either way the step number keeps meaning "distance from background toward foreground".

Does OKLCH feel like the right level to work at, or would you rather start simpler with an HSL ramp and refine later?

For distinct hues there isn't one universal "the standard", but a few are genuinely well-regarded references, and which fits depends on whether you weight semantic convention or maximal distinctiveness:

• Open Color — open-source, built specifically for UI, 13 hues each with 10 perceptually-tuned shades. The closest thing to a "just use this" answer for general web UI.
• Radix Colors — 12-step scales with light/dark pairs already solved; hues chosen to be distinguishable. Great if you want the dark-mode inversion handled for you conceptually.
• ColorBrewer (qualitative sets) — the gold standard when the priority is distinctness and colourblind-safety, though it's aimed at data viz rather than UI roles.

Given your role-driven plan (neutral + the semantic six), the pragmatic path is to anchor the four conventional ones to their expected hues and space the rest evenly around the wheel:

• col1 neutral — gray (hue barely matters; pick a slightly cool or warm gray)
• col2 primary — blue ~250 (the safe brand default)
• col3 danger — red ~25
• col4 warning — amber ~75
• col5 success — green ~145
• col6 info — cyan ~220
• col7 secondary — violet ~300

Those hue angles are roughly evenly distributed (except where convention pins them), so the seven stay mutually distinguishable. Since we're working in OKLCH, the hue numbers above drop straight into the H slot and we reuse the same L/C arch for every column.

Want to go with that role-anchored set as the starting theme, or start from an existing palette like Open Color and adapt its hues to our 7-slot layout?

Let's generate it. We define the shared L and C arches, the per-column hues, then build the :root block:

{
  "id": "toolu_01WHzp1fcC6YaFDMsFDoV7ME",
  "server": false,
  "call": {
    "function": "add_msg",
    "arguments": {
      "content": "hues = dict(col1=250, col2=250, col3=25, col4=75, col5=145, col6=220, col7=300)\nls = [0.97,0.90,0.80,0.68,0.55,0.43,0.30]\ncs = [0.03,0.07,0.12,0.18,0.20,0.17,0.12]\ndef col_var(n,i,l,c,h): return f\"  --{n}{i+1}: oklch({l} {c} {h});\"",
      "msg_type": "code",
      "placement": "add_after"
    }
  },
  "result": "_d86e3221"
}

{
  "id": "toolu_01FkJnn9mFr3jGt5Gx6UpXHf",
  "server": false,
  "call": {
    "function": "add_msg",
    "arguments": {
      "content": "lines = [col_var(n,i,ls[i],0 if n=='col1' else cs[i],h) for n,h in hues.items() for i in range(7)]\ncss = \":root {\\n\" + \"\\n\".join(lines) + \"\\n}\"\nprint(css)",
      "msg_type": "code",
      "id": "_d86e3221",
      "placement": "add_after"
    }
  },
  "result": "_571504b7"
}

I've added two cells: the first defines the hues map, the ls/cs arches, and a col_var helper; the second builds the :root block (forcing chroma to 0 for col1 so neutral stays a true gray) and prints it. Give them a run and we can eyeball the output.

It really does! The OKLCH approach paid off — look at how the lightness marches down evenly across every column, so row 4 reads as "mid" for every hue, not just some. That's the perceptual uniformity doing its job.

A few things worth noticing in your grid:

• col1 (neutral) is a clean true gray since we zeroed its chroma — no colour cast creeping in.
• The chroma arch shows up nicely: the lightest tints (row 1) and darkest shades (row 7) stay calm, while the vivid middle (rows 4–5) carries the punch. No muddy darks, no washed-out mids.
• All seven hues stay mutually distinct at every lightness level, which was the goal.

This is a solid base theme. The next natural step whenever you're ready is the role layer — mapping --danger: var(--col34) and friends — plus deciding your fg/bg anchors.

Totally reasonable — max contrast is a defensible default, and it keeps the theme author in control. Pure black/white as the anchors:

{
  "id": "toolu_01VxLsEU1LHRnHCvdecvUMNS",
  "server": false,
  "call": {
    "function": "add_msg",
    "arguments": {
      "content": "extra = \"  --bg: #fff;\\n  --fg: #000;\"\ncss = \":root {\\n\" + extra + \"\\n\" + \"\\n\".join(lines) + \"\\n}\"\nStyle(css)",
      "msg_type": "code",
      "placement": "add_after"
    }
  },
  "result": "_29ab99c6"
}

Added a cell that prepends --bg: #fff and --fg: #000 to the :root block. Run it and you'll have your pure black/white anchors sitting alongside the seven hue columns.

You're right, let's discuss before writing anything.

The role layer maps semantic names onto positions. The open questions I see:

1. Which prominence step does each role default to? A role like danger for a button background needs a step that's vivid enough to read as alarming but dark enough for white text to sit on it — probably step 4 or 5. So --danger: var(--col34). But...

2. Does a role need one value or several? A danger button wants a solid fill (~step 4), but a danger alert box might want a pale tint background (step 1) with dark danger text (step 6). So a single --danger often isn't enough — you tend to end up with something like --danger, --danger-bg, --danger-fg (or a subtle/bold pair).

3. Where does neutral fit? Text, borders, and surfaces all come from col1. Those are arguably the most-used roles of all — --fg/--bg you've pinned to pure black/white, but you'll likely want --border, --surface, --muted (dimmed text) pulling from neutral's mid steps.

So before mapping, the key decision is: how rich is a "role"? Is it a single colour, or a little bundle (fill / on-fill / subtle-bg)?

My instinct: start with the simplest thing that works — each semantic role points at a single "solid" step (the fill), and we add -bg/-fg variants only when a component actually needs them. Matches the incremental spirit you've been working in.

How rich do you want a role to be?

def swatch(i, bg): return Div(f"col3{i} danger text", style=f"color:var(--col3{i});background:{bg};padding:8px;font-weight:bold")
Div(*[swatch(i,'#000') for i in range(1,8)], *[swatch(i,'#fff') for i in range(1,8)])

This renders col31→col37 bold on black, then the same on white, so you can see which steps stay legible against each background.

Pretty much, yes — but with a nuance worth knowing.

col34 (L=0.68) is your peak-chroma-meets-mid-lightness step, so it's the most saturated, vivid red — which is exactly what "alert-y" means perceptually. The eye reads high chroma as urgency.

The nuance from standard wisdom: a single mid step like col34 looks alarming on both black and white, but it's usually not the one you'd use for the two most common danger jobs:

• Danger button fill (white text on red): you'd typically go a touch darker — col35 — so white text clears the ~4.5:1 contrast bar. col34 is often a hair too light for white text to pass.
• Danger text on a white page: col34 can be borderline for legibility; col35/col36 read as safer body text.

So col34 is the "warning light" colour — perfect when the red itself is the signal (an icon, a badge, a border, a focus ring). The darker steps are for when the red is a surface carrying text.

That actually reinforces the "a role is a little bundle" idea from earlier: danger as a vivid accent (col34) and danger as a text/fill colour (col35/36) genuinely want different steps.

def swatch(i, fg): return Div(f"col3{i} bg", style=f"background:var(--col3{i});color:{fg};padding:8px;font-weight:bold")
Div(*[swatch(i,'#000') for i in range(1,8)], *[swatch(i,'#fff') for i in range(1,8)], style='display:flex')

This shows black text over col31→col37 backgrounds, then white text over the same, so you can see which steps each text colour sits on comfortably.

Yes — there's standard vocabulary for exactly this. What you're describing is the well-trodden subtle / default / bold triad (Material calls it the "container" model, GitHub Primer calls the strong one "emphasis"). The pattern recognises that one semantic role needs three surfaces, not one:

• --danger = col34 — the vivid accent: danger text/icon/border on the standard bg
• --danger-subtle (or -bg) = col33 — a soft tinted surface that takes default fg text (black here)
• --danger-bold (or -emphasis/-solid) = col35 — a strong fill that takes contrasting text (white)

And the companion to that last one is the "on" colour — the text that rides on the bold fill:

• --on-danger = white (your --bg, effectively)

So "danger but with opposite-precedence text" is the bold/emphasis variant: col35 paired with --on-danger. That's the danger button; col33 is the danger alert box; col34 is danger as a signal (icon, ring, link).

The neat part for your theme-inversion: these are all role names, so the col-step mapping lives in the theme. Dark theme just redefines:

--danger: var(--col34);
--danger-subtle: var(--col35);
--danger-bold: var(--col33);
--on-danger: var(--fg);

Same four names, flipped steps — every component referencing --danger-bold keeps working untouched.

So the convention I'd suggest: each semantic role expands to {role}, {role}-subtle, {role}-bold, on-{role}. Start by defining only the ones a component actually needs, and fill in the rest as they come up.

Here's a generator for the role layer, mapping each semantic role to its column and expanding to the four-name triad+on:

roles = dict(neutral=1, primary=2, danger=3, warning=4, success=5, info=6, secondary=7)
def role_vars(r,n): return [f"  --{r}: var(--col{n}4);", f"  --{r}-subtle: var(--col{n}3);", f"  --{r}-bold: var(--col{n}5);", f"  --on-{r}: var(--bg);"]
rlines = [l for r,n in roles.items() for l in role_vars(r,n)]
print("\n".join(rlines))

Each role points at step 4 (accent), step 3 (subtle bg), step 5 (bold fill), and --bg for the on-colour — exactly the steps we validated with the danger swatches.

You're right — it's var(--bg) for all seven, so it carries no information. That's a direct consequence of OKLCH lightness being perceptual: every bold fill sits at L=0.55, so white clears contrast equally across all hues. There's no hue where the on-colour needs to flip.

So drop the per-role --on-* entirely. Two options:

• Just reference --bg directly in components (color: var(--bg) on a bold fill).
• Keep a single named handle --on-bold: var(--bg) if you'd like the intent documented in one place — useful only if some future theme makes bold fills light enough to need dark text, in which case that one line flips instead of seven.

I'd lean to the single --on-bold — it's one line, names the intent, and gives a theme author exactly one knob if they ever break the constant-contrast assumption.

def role_vars(r,n): return [f"  --{r}: var(--col{n}4);", f"  --{r}-subtle: var(--col{n}3);", f"  --{r}-bold: var(--col{n}5);"]
rlines = [l for r,n in roles.items() for l in role_vars(r,n)] + ["  --on-bold: var(--bg);"]
print("\n".join(rlines))

Dropped the per-role --on-*, kept the triad, and appended a single --on-bold at the end.

A clean way is to make one swatch-row function for a role, then render the whole set twice inside two themed wrappers — light keeps the :root mapping, dark is a scoped override that flips subtle↔bold and swaps bg/fg.

def role_row(r): return Div(Div('subtle',style=f"background:var(--{r}-subtle);color:var(--fg);padding:6px;flex:1"), Div(r,style=f"background:var(--{r});color:var(--on-bold);padding:6px;flex:1"), Div('bold',style=f"background:var(--{r}-bold);color:var(--on-bold);padding:6px;flex:1"), style="display:flex;font-weight:bold")
def roles_grid(): return Div(*[role_row(r) for r in roles], style="display:flex;flex-direction:column;gap:4px;width:320px;padding:12px")

For the dark override we generate flipped role vars (subtle=col5, bold=col3) plus inverted bg/fg, scoped to a .dark class:

def dark_vars(r,n): return [f"  --{r}-subtle: var(--col{n}5);", f"  --{r}-bold: var(--col{n}3);"]
dlines = ["  --bg:#000;", "  --fg:#fff;"] + [l for r,n in roles.items() for l in dark_vars(r,n)]
dark_css = ".dark {\n" + "\n".join(dlines) + "\n}"
print(dark_css)

Then show them side by side:

Div(roles_grid(), Div(roles_grid(), cls="dark", style="background:#000"), style="display:flex;gap:16px")

The base values (--neutral etc. at col4) stay put since the mid step works on either background; only the subtle/bold ends and bg/fg flip.

Good idea — that's the natural bridge from "design tokens" to "usable in markup". The one decision: a class name like .danger is ambiguous about which surface it means. Common convention is each role gives you a small family:

• .danger → bold fill + on-colour (the solid button look)
• .danger-subtle → subtle bg + normal fg (the alert-box look)
• .danger-text → just coloured text (the accent look)

That mirrors the three things we already validated. Here's a generator:

def role_cls(r): return [f".{r} {{ background:var(--{r}-bold); color:var(--on-bold); }}",
    f".{r}-subtle {{ background:var(--{r}-subtle); color:var(--fg); }}",
    f".{r}-text {{ color:var(--{r}); }}"]
clines = [l for r in roles for l in role_cls(r)]
print("\n".join(clines))

Each role expands to three classes pulling from the exact tokens we tested, so the classes inherit the light/dark flipping for free.

A few key ideas worth having in your head:

1. Use a scale, not arbitrary sizes. Pick a base (usually 1rem ≈ 16px) and multiply by a fixed ratio to step up/down. Common ratios: 1.2 (minor third, subtle), 1.25 (major third), 1.333 (perfect fourth, punchy). So each step is prev × ratio. This gives visual harmony for free, the same way your OKLCH lightness arch did for colour.

2. rem for sizes. rem is relative to the root font size, so if a user bumps their browser's default text size (accessibility!), everything scales. px ignores that wish; em compounds when nested (a 1.2em inside a 1.2em...). So rem is the safe default for a type scale.

3. line-height should be unitless. This is the big one, and it's where I'd diverge from Julia's file. She paired each size with an absolute line-height (--line-height-xs: 1rem). A unitless multiplier like 1.5 means "1.5× this element's font-size", so it scales correctly per size. An absolute value doesn't — a 1rem line-height on a giant heading would cramp it. Unitless also avoids an inheritance trap where children inherit the computed pixel value rather than the ratio.

4. Tighter line-height for big text, looser for small. Body text wants ~1.5 for readability; large headings want ~1.1–1.2 (long lines of huge text with airy spacing look disconnected). So line-height isn't one constant — it loosens as size shrinks.

So your instinct is right, with one refinement: define a handful of sizes (as a ratio-based scale in rem), and a couple of unitless line-height multipliers (say tight for headings, normal for body) — rather than one line-height per size. That's fewer vars and they compose better.

Want to pick a base + ratio and generate the size scale, the same code-gen way we did colours?

You're largely right, with some nuance.

Traditional print body text typically runs tighter than the web's 1.5 — books and newspapers commonly sit around 1.2–1.4 (in typographic terms, "leading" of a few points over the type size). Dense newspaper columns especially trended tight, partly to fit more text per column inch.

But there are a few confounds worth knowing:

• Line length interacts with line-height. The narrower the column, the tighter you can set the leading without the eye losing its place returning to the next line. Newspapers used very narrow columns (a few words wide), which is exactly the condition where tight leading reads fine. The web's 1.5 convention assumes wider measures (60–75 characters), where looser leading helps the return sweep. So the rule isn't "print = tight, web = loose" so much as "long lines need more leading than short lines."

• Ink and contrast. Black ink on cream paper has gentler contrast than #000 on #fff screens. Your max-contrast pure-black-on-white choice actually pushes slightly toward wanting a touch more breathing room than print did, since high contrast makes tight lines feel more crowded.

• x-height of the typeface. Fonts with large x-heights (most screen fonts) look more crowded at a given line-height than the smaller-x-height faces common in book printing, so they tend to want a bit more leading to feel equivalent.

So your preference for denser is well-founded and historically grounded — just bear in mind that if you go tight, you'll want to keep your line length shorter to match (which dovetails with Julia's --inner-width column idea). A reasonable dense-but-safe body might be ~1.4 rather than 1.5, going tighter (~1.15–1.25) for headings.

1.3 is a sensible spot — it sits right in that classic book/newspaper band we just talked about, denser than the web's reflexive 1.5 but still open enough to avoid lines visually colliding. Given your other choices it's especially coherent: max contrast and a constrained column width are exactly the conditions where 1.3 reads cleanly, since shorter lines don't need the extra leading to guide the return sweep.

A reasonable plan then: 1.3 for prose/body, and step down a touch for large headings (~1.15) where tighter looks more deliberate. We can fold those into the type scale as two unitless multipliers whenever you're ready to generate it.

There's reasonable consensus now, and it breaks down by what you're sizing:

rem — the default for most things. Font sizes especially. Because rem is relative to the root, it respects the user's browser font-size preference (a real accessibility win) without the compounding problem em has. Use it for type scales, and increasingly for spacing/layout too so the whole UI scales with user preference.

em — when you want sizing relative to the current element's font-size. Its compounding (each nested level multiplies) is a bug for font-size but a feature for properties that should track the local text. Classic uses:

• padding/margin on a button that should grow with the button's own text
• line-height (though there you usually want it unitless, which is subtly different again)
• a ::before icon sized in em so it matches whatever text it sits beside

So em shines for "this should scale with this component's font", which is exactly the badge/button pattern you've been building.

px — when you genuinely want a fixed, non-scaling value. Consensus has softened here; it's fine for things that aren't really "type" and shouldn't scale:

• borders (1px solid — a hairline should stay a hairline)
• the root font-size itself is best not set in px (or left unset) so you don't override the user's preference
• occasionally box-shadows, fine positioning, tiny radii

The one near-universal "don't": avoid px for font-size, because it silently overrides users who've bumped their default text size.

Here's a Tailwind-aligned scale, with line-heights that tighten as size grows (anchored on your 1.3 prose preference):

sizes = dict(xs=0.75, sm=0.875, base=1.0, lg=1.125, xl=1.25, xl2=1.5, xl3=1.875, xl4=2.5)
lhs   = dict(xs=1.4,  sm=1.35,   base=1.3, lg=1.3,   xl=1.25, xl2=1.2,  xl3=1.15,  xl4=1.1)

The idea: tiny text gets the airiest leading since short glyphs on long lines need help; body/base sits at your 1.3; and the big display sizes tighten toward 1.1 where dense looks deliberate.

def size_var(k,v): return f"  --size-{k}: {v}rem;\n  --lh-{k}: {lhs[k]};"
szlines = [size_var(k,v) for k,v in sizes.items()]
def size_cls(k): return f".text-{k} {{ font-size:var(--size-{k}); line-height:var(--lh-{k}); }}"
szcls = [size_cls(k) for k in sizes]
print(":root {\n" + "\n".join(szlines) + "\n}\n" + "\n".join(szcls))

Each size gets a --size-* and matching --lh-* var, plus a .text-* class that sets both font-size and its paired line-height together.

{
  "id": "toolu_01RjikviBieNWp5rcRee1hVW",
  "server": false,
  "call": {
    "function": "add_msg",
    "arguments": {
      "content": "Div(*[P(f\"text-{k} — Sphinx of black quartz\", cls=f\"text-{k}\") for k in sizes], style=\"padding:12px\")",
      "msg_type": "code",
      "placement": "add_after"
    }
  },
  "result": "_6df23129"
}

Added a cell that renders one P per size with its .text-* class, each showing a sample line so you can eyeball the scale and the tightening line-heights together. You'll need P imported from fasthtml.components.

A few things we haven't touched that are worth knowing:

1. Fluid type with clamp(). Instead of fixed rem sizes plus breakpoints, clamp(min, preferred, max) lets a size scale smoothly with viewport width. E.g. clamp(1.5rem, 1rem + 2vw, 2.5rem) grows a heading as the window widens, then stops at the bounds. Great for big display sizes; usually overkill for body text. This is the "fluid type" idea behind tools like Utopia.

2. Line length (the "measure"). Already came up via your column width, but it's a typographic control too: ~60–75 characters is the readability sweet spot, set with max-width in ch units (max-width: 66ch), where 1ch ≈ one character's width. Pairs naturally with your dense 1.3 leading.

3. Letter-spacing (tracking) at the extremes. Big headings often look better very slightly tightened (letter-spacing: -0.02em); tiny all-caps labels benefit from loosening (+0.05em). Subtle, but it's the polish layer on a type scale.

4. A couple of useful font properties:

• text-wrap: balance — evens out ragged headings across lines (modern, well-supported now).
• font-variant-numeric: tabular-nums — equal-width digits, handy for your badge counts or tables so numbers don't jiggle.

Of these, the measure (ch-based max-width) is the one I'd fold into the system next, since it directly supports your dense-leading choice. The rest are per-component polish you can reach for as needed.

clamp(min, preferred, max) picks the preferred value, but never lets it go below min or above max. So it's effectively max(min, min(preferred, max)).

Taking clamp(1.5rem, 1rem + 2vw, 2.5rem):

• min = 1.5rem — the floor. On narrow screens the size never drops below this.
• preferred = 1rem + 2vw — the "live" value that tracks viewport width. 2vw is 2% of the viewport width, and the 1rem base keeps it from getting too tiny at the low end. As the window widens, this term grows.
• max = 2.5rem — the ceiling. On wide screens the size stops growing here.

So the heading sits at 1.5rem on a phone, grows smoothly as the viewport widens (driven by the vw term), then caps at 2.5rem on a big monitor. The vw in the middle is what makes it fluid — without a vw (or %/vh) term there, clamp would just be a static pick and the smooth scaling wouldn't happen.

One gotcha: using vw alone as the preferred (e.g. 4vw) makes text scale only with viewport, which can hurt accessibility since it ignores the user's zoom/font preference. Mixing in a rem term (the 1rem + part) keeps it partly tied to user settings, which is the recommended pattern.

Based on what actually gets used heavily in real Tailwind codebases, the high-value utilities cluster into a few groups:

Flexbox/layout (by far the most used) — these dominate real markup:

• flex, items-center, justify-between, gap-* — the workhorse combo for rows of things (toolbars, nav, card headers)
• grid, grid-cols-* — for actual grids

Spacing — the single most-typed utilities:

• gap-* (on flex/grid parents — the "no outer margin" friendly way to space children, matching that article from earlier)
• the occasional p-* for padding inside bordered/filled surfaces

The accessibility staple:

• .sr-only — visually hidden but readable by screen readers (Julia mentioned this one). Genuinely useful and you can't easily reproduce it ad-hoc.

A handful of "can't easily do inline" helpers:

• truncate (ellipsis overflow — fiddly to remember: needs three properties together)
• hidden / display toggles
• sr-only's visual cousin for focus states

The interesting pattern from practice: people think they need hundreds of utilities, but the 80/20 reality is that flex + gap + items/justify-center covers the overwhelming majority of layout, and the rest are occasional reaches.

For your foundation, I'd suggest the small careful set Julia hints at: .sr-only, a flex helper or two, and truncate — the things that bundle multiple properties you'd hate to retype. Things like a single gap or padding are arguably better left to the component, since they're one property and context-specific.

Which would you like to start with?

Here are the ones worth baking in — each bundles properties you'd hate to retype:

.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}
.truncate { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.row { display: flex; align-items: center; }
.row-between { display: flex; align-items: center; justify-content: space-between; }
.hidden { display: none; }

.sr-only hides content visually but keeps it for screen readers; .truncate is the three-property ellipsis combo; .row/.row-between cover the most common flex layouts; .hidden is a plain display toggle.

A simple cell magic that wraps the cell body in a <style> and displays it:

from IPython.core.magic import register_cell_magic

@register_cell_magic
def css(line, cell): display(HTML(f"<style>{cell}</style>"))