Many more Markdown extensions and formatting improvements.

docs/design-principles.md

@@ -19,8 +19,8 @@ Pagerite is a single-user CMS/blog. This document records the initial high-level
 
 - Content is written in **Markdown** with powerful extensions (tables, footnotes, code highlighting, etc.).
 - **Embedded HTML is passed through unfiltered**, including inline scripts and other dynamic content the author wants to post. This is safe by the single-trusted-author assumption above.
-- Renderer: **markdown-it-py** with mdit-py-plugins (footnotes, definition lists, task lists, brace-attributes; tables and strikethrough from the default preset), with `html=True` for raw passthrough, `typographer=True` for SmartyPants-style replacements in body text (curly quotes, `--` / `---` → en / em dashes, `...` → ellipsis, `(c)` → ©, etc.), and `breaks=True` so single line breaks inside paragraphs become `<br>`. Code spans/blocks and raw HTML are left untouched. Fenced code blocks are highlighted server-side with **Pygments** (`nowrap` spans styled by `/_assets/pygments-*.css`, which maps every token class onto the `--code-*` variables; the base stylesheet defines light and dark palette sets resolved via `light-dark()`, so each theme gets the set matching its `color-scheme` and may only retint `--code-bg` to keep the well in the page's color family); a JS copy button appears on hover. Should this prove limiting, we implement our own renderer on top of html5tagger, which we already use for all HTML generation.
-- **Files are content-addressed.** Uploads (`PUT /_api/files/{filename}`) are stored by content hash — blake3, first 6 bytes hex + original extension — and served immutable from `/_f/{hash}.ext`. Absolute URLs that survive page renames and dedupe identical content; pages no longer own files. An image standing alone in its paragraph becomes a block `<figure>` — with `<figcaption>` when it has a title; images inline with text and raw `<img>` HTML stay plain inline images. Positioning is by attribute classes: `![alt](/_f/….avif "Caption"){.right}` — `{.right}`, `{.left}` float at 30% of the text column (the caption wraps within it; an explicit `width=300` makes the figure shrink-wrap the image instead), `{.wide}` goes full bleed (viewport edge to edge, or up to the docked editor; the sidebar stacks on top of it); plain attributes like `width=300` work too. Headings (h1/h2) clear floats, so images never overflow into the next section.
+- Renderer: **markdown-it-py** with mdit-py-plugins (footnotes, definition lists, task lists, brace-attributes, admonitions and `::: name` containers — generic `<div class="name">` wrappers, of which `::: aside` floats as a muted side box (leaning into the empty right gutter on wide single-column pages) and `::: nocols` opts its section out of column layout; tables and strikethrough from the default preset), GitHub-style alerts (`> [!NOTE]` / TIP / IMPORTANT / WARNING / CAUTION, rendered in the admonition callout styling), with `html=True` for raw passthrough, `typographer=True` for SmartyPants-style replacements in body text (curly quotes, `--` / `---` → en / em dashes, `...` → ellipsis, `(c)` → ©, etc.), and `breaks=True` so single line breaks inside paragraphs become `<br>` — including inside blockquotes, where every newline is kept and a blank `>` line starts a new paragraph. Code spans/blocks and raw HTML are left untouched. Fenced code blocks are highlighted server-side with **Pygments** (`nowrap` spans styled by `/_assets/pygments-*.css`, which maps every token class onto the `--code-*` variables; the base stylesheet defines light and dark palette sets resolved via `light-dark()`, so each theme gets the set matching its `color-scheme` and may only retint `--code-bg` to keep the well in the page's color family); a JS copy button appears on hover. Should this prove limiting, we implement our own renderer on top of html5tagger, which we already use for all HTML generation.
+- **Files are content-addressed.** Uploads (`PUT /_api/files/{filename}`) are stored by content hash — blake3, first 6 bytes hex + original extension — and served immutable from `/_f/{hash}.ext`. Absolute URLs that survive page renames and dedupe identical content; pages no longer own files. An image standing alone in its paragraph becomes a block `<figure>` — with `<figcaption>` when it has a title; images inline with text and raw `<img>` HTML stay plain inline images. Positioning is by attribute classes: `![alt](/_f/….avif "Caption"){.right}` — `{.right}`, `{.left}` float at 30% of the text column (the caption wraps within it; an explicit `width=300` makes the figure shrink-wrap the image instead), `{.wide}` goes full bleed (viewport edge to edge, or up to the docked editor; the sidebar stacks on top of it); plain attributes like `width=300` work too. The same brace syntax on a block's last line (no blank line between) applies to the whole block: a paragraph ending with `{.wide}` becomes a full-width element that breaks out of the column layout. Headings (h1/h2) clear floats, so images never overflow into the next section.
 
 ## Page structure and navigation
 
@@ -34,7 +34,7 @@ Pagerite is a single-user CMS/blog. This document records the initial high-level
 
 ## Reading experience
 
-- The article column is sized by the **viewport, never by content**: a symmetric grid (`1fr minmax(0, 78rem) 1fr`) with flexible gutters keeps the layout stable across navigation. The sidebar occupies the left gutter, the right gutter balances it; wide screens get columns inside long articles without changing the article's width.
+- The article column is sized by the **viewport, never by content**: a symmetric grid (`1fr minmax(0, 78rem) 1fr`) with flexible gutters keeps the layout stable across navigation. The sidebar occupies the left gutter, the right gutter balances it; wide screens get columns inside long articles without changing the article's width. Columns are decided client-side (pagerite.js): the body splits into segments at h1/h2 headings and `.wide` elements (full-width separators, never inside columns), and a segment gets columns only when it holds enough text — code blocks are excluded from that measure, and a `::: nocols` container opts its whole section out.
 - A gentle **scroll-reveal** of headings, figures and block-level elements (IntersectionObserver). It is layout-level: articles need no support for it, and `prefers-reduced-motion` disables all motion.
 
 ## Styling

frontend/src/TransitionGraph.vue

@@ -8,7 +8,7 @@
  */
 import { computed, onBeforeUnmount, onMounted, shallowRef, watch } from 'vue'
 import { DAY } from './analytics/time.js'
-import { formatCount } from './analytics/format.js'
+import { formatCount, formatReadTime } from './analytics/format.js'
 import {
   TNODE_W,
   TNODE_H,
@@ -151,7 +151,7 @@ onBeforeUnmount(() => cancelAnimationFrame(rafId))
 const fitsPill = (label, fontPx = 19) => label.length * 0.52 * fontPx <= TNODE_W - 16
 
 const countLabel = (n) =>
-  n.readMin ? `${formatCount(n.views)}×${n.readMin}m` : formatCount(n.views)
+  n.readSec ? `${formatCount(n.views)}×${formatReadTime(n.readSec)}` : formatCount(n.views)
 </script>
 
 <template>

frontend/src/analytics/transitions.js

@@ -259,8 +259,8 @@ function sortByNav(root, navOrder) {
   walk(root)
 }
 
-/** Compute median reading time per article in whole minutes. */
-function buildReadMinutes(visits) {
+/** Compute median reading time per article in seconds. */
+function buildReadSeconds(visits) {
   const times = {}
   for (const v of visits || []) {
     for (const [path, sec] of Object.entries(v.read || {})) {
@@ -269,19 +269,19 @@ function buildReadMinutes(visits) {
       }
     }
   }
-  const minutes = {}
+  const seconds = {}
   for (const [path, arr] of Object.entries(times)) {
     arr.sort((a, b) => a - b)
     const mid = Math.floor(arr.length / 2)
     const median =
       arr.length % 2 ? arr[mid] : (arr[mid - 1] + arr[mid]) / 2
-    minutes[path] = Math.max(1, Math.round(median / 60))
+    seconds[path] = Math.round(median)
   }
-  return minutes
+  return seconds
 }
 
 /** Compute view counts, labels and hidden flags for each node. */
-function annotateNodes(nodes, viewsData, titles, readMinutes) {
+function annotateNodes(nodes, viewsData, titles, readSeconds) {
   const viewCount = (p) => {
     let n = 0
     for (const c of Object.values(viewsData?.[p] || {})) n += c
@@ -290,7 +290,7 @@ function annotateNodes(nodes, viewsData, titles, readMinutes) {
 
   for (const n of nodes) {
     n.views = viewCount(n.path)
-    n.readMin = readMinutes[n.path] || 0
+    n.readSec = readSeconds[n.path] || 0
     // Article title inside the pill (clipped at the pill border on
     // render), slug as fallback for pages missing from the site tree.
     n.label = titles.get(n.path) || (n.path === '/' ? '🏠︎' : n.path.split('/').pop())
@@ -895,13 +895,13 @@ export function buildTransitionGraph(data, pageTree, visits = [], dayScale = 1)
   const exits = collectExitPairs(data?.transitions)
   const navOrder = buildNavigationOrder(pageTree)
   const titles = buildTitleMap(pageTree)
-  const readMinutes = buildReadMinutes(visits)
+  const readSeconds = buildReadSeconds(visits)
 
   if (!internal.length && !navOrder.size) return null
 
   const { nodes, byPath, root } = buildNodeTree(internal, navOrder)
   sortByNav(root, navOrder)
-  annotateNodes(nodes, data?.views, titles, readMinutes)
+  annotateNodes(nodes, data?.views, titles, readSeconds)
   const { arcs, arcLeft } = layoutGroups(root)
   const placed = nodes.filter((n) => !n.hidden)
   const pairs = aggregatePairs(internal)

frontend/src/assets/pagerite.css

@@ -65,6 +65,11 @@
   box-sizing: border-box;
 }
 
+::selection {
+  background: color-mix(var(--accent) 30%, transparent);
+  color: inherit;
+}
+
 /* Links never underline — including SVG link text, which the UA stylesheet
    underlines by default. */
 a {
@@ -126,7 +131,10 @@ body {
   display: flex;
   flex-direction: column;
   justify-content: flex-end;
-  height: 13rem;
+  /* Height scales down proportionally on small screens: 13rem at 800px
+     (50rem) viewport, shrinking with the smaller of viewport width/height
+     (vmin) below that, floored at 8rem. */
+  height: clamp(8rem, 26vmin, 13rem);
   box-sizing: content-box;
   background: linear-gradient(135deg, var(--surface), var(--bg));
   border-bottom: 1px solid var(--line);
@@ -192,7 +200,9 @@ body {
 #brand {
   font-family: var(--font-brand);
   font-weight: 700;
-  font-size: 2.4rem;
+  /* Scales down proportionally on small screens, same curve as the banner
+     height: 2.4rem at 800px, shrinking with vmin below that. */
+  font-size: clamp(1.4rem, 4.8vmin, 2.4rem);
   text-decoration: none;
   /* One line always: pagerite.js shrinks the font size to fit instead of
      wrapping (the themed size is the maximum). */
@@ -295,9 +305,10 @@ body.editing #sidebar {
   bottom: 0;
   left: 0;
   width: var(--editor-w);
-  /* Above the sidebar and .edit-link while sliding in/out (the host now
-     lives at the end of <body>, so it needs its own stacking level). */
-  z-index: 3;
+  /* Above the sidebar, .edit-link and the banner's top-right pens
+     (z-index 10) while sliding in/out (the host now lives at the end of
+     <body>, so it needs its own stacking level). */
+  z-index: 10;
 }
 
 .editor-root.overlay {
@@ -408,7 +419,10 @@ main {
 
 article h1,
 article h2,
-article h3 {
+article h3,
+article h4,
+article h5,
+article h6 {
   font-family: var(--font-heading);
   font-weight: 600;
   line-height: 1.25;
@@ -428,13 +442,31 @@ article dl,
 article blockquote,
 article pre,
 article figure,
-article table {
+article table,
+article h3,
+article h4,
+article h5,
+article h6 {
   margin-top: 0;
   margin-bottom: 1rem;
 }
 
-article h3 {
-  margin: 1.4rem 0 0.4rem;
+/* Headings separate from the text above via a top margin on the sibling
+   combinator: a heading that is the first child of a container (e.g. the
+   top of a .colseg column segment) gets no gap, and browsers truncate the
+   margin at column breaks, so column tops stay aligned. */
+article h3,
+article h4,
+article h5,
+article h6 {
+  margin-bottom: 0.4rem;
+}
+
+article * + h3,
+article * + h4,
+article * + h5,
+article * + h6 {
+  margin-top: 1.4rem;
 }
 
 /* Lists: small diamond emoji markers — blue 🔹 on odd nesting levels,
@@ -525,9 +557,10 @@ article dd {
 }
 
 /* Multi-column reading, but only for long articles (pagerite.js adds
-   .multicol based on content length and splits the body into .colseg segments
-   separated by full-width h2s and wide figures; only segments with enough
-   text get .cols). No fixed breakpoint: `columns: 30rem` lets CSS fit as
+   .multicol based on content length — code blocks excluded — and splits
+   the body into .colseg segments separated by full-width h2s and .wide
+   elements; only segments with enough text get .cols, and a ::: nocols
+   container opts its section out). No fixed breakpoint: `columns: 30rem` lets CSS fit as
    many columns of at least 30rem as the article's current width allows —
    since .multicol also uncaps the article width (see #content above), a
    wider window simply yields more columns. */
@@ -556,7 +589,9 @@ article dd {
   pre,
   blockquote,
   table,
-  dl {
+  dl,
+  .admonition,
+  .markdown-alert {
     break-inside: avoid;
   }
 }
@@ -576,10 +611,11 @@ article a:hover {
   color: var(--accent);
 }
 
-/* Blockquotes: inner paragraphs carry no margins (spacing comes from the
-   blockquote itself, bottom-only like everything else in articles). The
-   negative left margin pushes the bar out past the text edge, so quoted
-   text aligns with the surrounding paragraphs — same trick as code blocks. */
+/* Blockquotes: spacing comes from the blockquote itself (bottom-only like
+   everything else in articles); inner paragraphs keep only the gap between
+   them. The negative left margin pushes the bar out past the text edge, so
+   quoted text aligns with the surrounding paragraphs — same trick as code
+   blocks. */
 blockquote {
   margin: 0 0 1rem -0.5rem;
   padding: 0 0 0 0.25rem;
@@ -591,42 +627,128 @@ blockquote p {
   margin: 0;
 }
 
-/* Admonitions (markdown !!! note/warning/...): a lightweight callout in
-   the blockquote idiom — accent bar and a faint wash, recolored per type.
+blockquote p + p {
+  margin-top: 0.6rem;
+}
+
+/* Admonitions (markdown !!! note/warning/...) and GitHub-style alerts
+   (> [!NOTE] ...): a lightweight callout in the blockquote idiom — accent
+   bar and a faint wash, recolored per type, with a type emoji on the
+   title. The negative left margin pushes bar and wash out past the text
+   edge so the inner text aligns with surrounding paragraphs — same trick
+   as blockquotes and code blocks (margin-left = border + padding-left).
    Bottom-only margins like everything else in articles; inner paragraphs
    carry no margins of their own. */
-.admonition {
-  margin: 0 0 1rem;
+.admonition,
+.markdown-alert {
+  margin: 0 0 1rem -1.15rem;
   padding: 0.4rem 0.9rem;
   border-left: 0.25rem solid var(--admonition-color, var(--accent));
   border-radius: 0 0.3rem 0.3rem 0;
   background: color-mix(in srgb, var(--admonition-color, var(--accent)) 7%, transparent);
 }
 
-.admonition> :last-child {
+.admonition> :last-child,
+.markdown-alert> :last-child {
   margin-bottom: 0;
 }
 
-.admonition-title {
+.admonition-title,
+.markdown-alert-title {
   margin: 0 0 0.2rem;
   font-weight: 600;
   color: var(--admonition-color, var(--accent));
 }
 
+.admonition-title::before,
+.markdown-alert-title::before {
+  padding-right: 0.35em;
+}
+
+.admonition.note .admonition-title::before,
+.markdown-alert-note .markdown-alert-title::before {
+  content: "ℹ️";
+}
+
+.admonition.tip .admonition-title::before,
+.admonition.hint .admonition-title::before,
+.markdown-alert-tip .markdown-alert-title::before {
+  content: "✨";
+}
+
+.admonition.important .admonition-title::before,
+.markdown-alert-important .markdown-alert-title::before {
+  content: "❗";
+}
+
+.admonition.success .admonition-title::before {
+  content: "✅";
+}
+
+.admonition.warning .admonition-title::before,
+.markdown-alert-warning .markdown-alert-title::before {
+  content: "⚠️";
+}
+
+.admonition.caution .admonition-title::before,
+.markdown-alert-caution .markdown-alert-title::before {
+  content: "🔥";
+}
+
+.admonition.danger .admonition-title::before,
+.admonition.failure .admonition-title::before {
+  content: "⛔";
+}
+
 .admonition.tip,
 .admonition.important,
 .admonition.hint,
-.admonition.success {
+.admonition.success,
+.markdown-alert-tip,
+.markdown-alert-important {
   --admonition-color: var(--accent2);
 }
 
 .admonition.warning,
 .admonition.caution,
 .admonition.danger,
-.admonition.failure {
+.admonition.failure,
+.markdown-alert-warning,
+.markdown-alert-caution {
   --admonition-color: var(--accent3);
 }
 
+/* Asides (::: aside): a floated side box in the floated-figure idiom;
+   consecutive asides stack (clear: right). On wide single-column pages it
+   leans into the empty right gutter (below 104rem the gutter cannot hold
+   the box; multicol pages have no right gutter at all, and while editing
+   the docked panel reshapes the gutters — in all these it stays a plain
+   float). Headings already clear floats, so asides never bleed into the
+   next section. */
+.aside {
+  float: right;
+  clear: right;
+  width: 30%;
+  max-width: 20rem;
+  margin: 0.3rem 0 1rem 1.2rem;
+  padding: 0.6rem 0.9rem;
+  font-size: 0.9rem;
+  color: var(--muted);
+  background: color-mix(in srgb, var(--accent) 6%, transparent);
+  border-radius: 0.3rem;
+}
+
+.aside> :last-child {
+  margin-bottom: 0;
+}
+
+@media (min-width: 104rem) {
+  body:not(.editing):not(:has(.multicol)) .aside {
+    width: 12rem;
+    margin-right: -13rem;
+  }
+}
+
 pre {
   overflow-x: auto;
   padding: 0.5rem 0.8rem;
@@ -931,6 +1053,17 @@ article h2 {
     gap: 0.15rem 0.9rem;
   }
 
+  /* The editor panel takes over the entire viewport: no space left for
+     the banner or the page content (main.js pins its top to 0 at these
+     widths). */
+  body.editing #content {
+    margin-left: 0;
+  }
+
+  .editor-host {
+    width: 100vw;
+  }
+
   #content {
     display: flex;
     flex-direction: column;

frontend/src/main.js

@@ -51,10 +51,15 @@ function setEditingClass(enable) {
 // the page: its top is the banner's bottom edge while the banner is visible
 // (= #content's top edge), and the viewport top once the banner has
 // scrolled away. The window keeps scrolling normally while editing.
+// Below 48rem the panel covers the entire viewport (pagerite.css), so its
+// top stays 0 regardless of the banner.
+const narrow = matchMedia('(max-width: 48rem)')
 function trackPanelTop() {
   const content = document.getElementById('content')
   if (host && content) {
-    host.style.top = `${Math.max(0, content.getBoundingClientRect().top)}px`
+    host.style.top = narrow.matches
+      ? '0px'
+      : `${Math.max(0, content.getBoundingClientRect().top)}px`
   }
 }
 

frontend/src/pagerite.js

@@ -277,23 +277,32 @@ import "overlayscrollbars/overlayscrollbars.css";
   });
 
   // Multi-column layout only when there is enough text to justify it.
-  // Split the body into columned segments: h1s, h2s and wide figures are
+  // Split the body into columned segments: h1s, h2s and wide elements are
   // full-width separators and never go inside columns.
   function applyMulticol(main) {
     const article = main.querySelector("article");
     if (!article) return;
     const body = article.querySelector(".body");
+    // Code blocks don't read as flowing text and are often generated
+    // filler; exclude them when measuring whether the text justifies
+    // columns.
+    const textLen = (el) => {
+      let n = el.textContent.trim().length;
+      for (const pre of el.querySelectorAll("pre")) n -= pre.textContent.length;
+      return n;
+    };
     article.classList.toggle(
       "multicol",
-      !!body && body.textContent.trim().length > 1800,
+      !!body && textLen(body) > 1800,
     );
     if (body && article.classList.contains("multicol")
         && !body.querySelector(".colseg")) {
-      // h1s, h2s and anything holding a wide image are full-width
-      // separators
+      // h1s, h2s and wide elements (a {.wide} block or anything holding
+      // one, e.g. a figure with a wide image) are full-width separators
       const isSeparator = (el) =>
         el.tagName === "H1" || el.tagName === "H2"
-        || el.querySelector("img.wide") !== null;
+        || el.classList.contains("wide")
+        || el.querySelector(".wide") !== null;
       let seg = null;
       for (const el of [...body.children]) {
         if (isSeparator(el)) {
@@ -309,9 +318,13 @@ import "overlayscrollbars/overlayscrollbars.css";
         }
       }
       // Columns are per section: only segments with enough text get them,
-      // so a short ingress or a brief section stays single-column.
+      // so a short ingress or a brief section stays single-column. A
+      // .nocols container (::: nocols) opts its whole section out.
       for (const s of body.querySelectorAll(".colseg")) {
-        s.classList.toggle("cols", s.textContent.trim().length > 600);
+        s.classList.toggle(
+          "cols",
+          s.querySelector(".nocols") === null && textLen(s) > 600,
+        );
       }
     }
   }

pagerite/markdown.py

@@ -4,8 +4,17 @@ Raw HTML (including inline scripts) is passed through unfiltered: the
 single author is trusted. Extensions: tables and strikethrough (from the
 "default" preset), footnotes, definition lists, task lists,
 brace-attributes (`{.class width=300}` on any element, images in
-particular) and admonitions (``!!! note Title`` with an indented body —
-note/tip/warning/etc., the title optional). Bare URLs autolink (GFM), with
+particular), admonitions (``!!! note Title`` with an indented body —
+note/tip/warning/etc., the title optional) and GitHub-style alerts
+(``> [!NOTE]`` / TIP / IMPORTANT / WARNING / CAUTION, rendered in the
+same callout styling). ``::: name`` opens a generic container rendered
+as ``<div class="name">`` and closed by a matching ``:::`` (nest by
+giving the outer container more colons, e.g. `::::`); ``::: aside``
+floats as a side box beside the text and ``::: nocols`` opts its
+section out of the column layout. A brace-attribute
+line as a block's last line (no blank line between) applies to the whole
+block, e.g. a paragraph ending with ``{.wide}`` breaks out of the column
+layout as a full-width element. Bare URLs autolink (GFM), with
 the ``https://`` scheme hidden in the link text (``http://`` and other
 schemes stay visible; manually labelled links are untouched), and
 ``H~2~O`` / ``x^2^`` give sub/superscripts.
@@ -33,6 +42,8 @@ from markdown_it.common.utils import escapeHtml
 from markdown_it.renderer import RendererHTML
 from mdit_py_plugins.admon import admon_plugin
 from mdit_py_plugins.attrs import attrs_plugin
+from mdit_py_plugins.attrs.parse import ParseError, parse as parse_attrs
+from mdit_py_plugins.container import container_plugin
 from mdit_py_plugins.deflist import deflist_plugin
 from mdit_py_plugins.footnote import footnote_plugin
 from mdit_py_plugins.gfm_autolink import gfm_autolink_plugin
@@ -107,6 +118,14 @@ def _unwrap_lone_figures(state) -> None:
         if child and child.type == "image":
             if (tokens[i - 1].type == "paragraph_open"
                     and tokens[i + 1].type == "paragraph_close"):
+                # A lone image becomes a <figure> (see _image_rule); block
+                # attrs on the paragraph (e.g. a trailing {.wide} line) move
+                # onto the image so they survive the unwrap.
+                for key, value in (tokens[i - 1].attrs or {}).items():
+                    if key == "class":
+                        child.attrJoin("class", value)
+                    else:
+                        child.attrSet(key, value)
                 tokens[i - 1].hidden = True
                 tokens[i + 1].hidden = True
 
@@ -149,6 +168,72 @@ def _shorten_autolinks(state) -> None:
                     text.content = text.content.removeprefix("https://")
 
 
+_CONTAINER_NAME_RE = re.compile(r"\s*[a-zA-Z][\w-]*\s*$")
+
+
+def _container_render(self, tokens, idx, options, env):
+    """Render `::: name` containers as `<div class="name">`."""
+    token = tokens[idx]
+    if token.nesting == 1:
+        token.attrJoin("class", token.info.strip())
+    return self.renderToken(tokens, idx, options, env)
+
+
+def _block_attrs(state) -> None:
+    """Apply `{.class key=value}` on a block's last line to the block.
+
+    The inline attrs plugin only covers attributes right after an image,
+    code span or link; this extends the same brace syntax to whole blocks,
+    e.g. a paragraph ending with a `{.wide}` line (no blank line between)
+    gets the `wide` class and thereby breaks out of the column layout.
+    A lone `{...}` paragraph applies to the previous block instead (this
+    is how headings take attributes, since a heading's next line always
+    starts a new paragraph). Runs before the typographer so quotes inside
+    attributes stay straight.
+    """
+    tokens = state.tokens
+    for i, token in enumerate(tokens):
+        if token.type != "inline" or not token.children:
+            continue
+        text = token.children[-1]
+        if (text.type != "text" or not text.content.startswith("{")
+                or not text.content.endswith("}")):
+            continue
+        try:
+            _, attrs = parse_attrs(text.content.strip())
+        except ParseError:
+            continue
+        standalone = len(token.children) == 1
+        if not standalone and token.children[-2].type != "softbreak":
+            continue
+        # The target: the enclosing block for a trailing attrs line, or the
+        # previous same-level block for a standalone attrs paragraph. Never
+        # a hidden token (tight-list paragraphs render no tag to hold the
+        # attributes) — in that case leave the text untouched instead of
+        # silently swallowing it.
+        own = i - 1  # standalone: the attrs paragraph's own opening token
+        j = i - 1
+        while j >= 0:
+            if (tokens[j].nesting == 1 and not tokens[j].hidden
+                    and (not standalone or (j != own
+                                            and tokens[j].level == tokens[own].level))):
+                break
+            j -= 1
+        if j < 0:
+            continue
+        for key, value in attrs.items():
+            if key == "class":
+                tokens[j].attrJoin("class", value)
+            else:
+                tokens[j].attrSet(key, value)
+        if standalone:
+            tokens[own].hidden = True
+            token.children = []
+            tokens[i + 1].hidden = True
+        else:
+            del token.children[-2:]
+
+
 md = (
     MarkdownIt(
         "default",
@@ -161,6 +246,8 @@ md = (
     )
     .use(attrs_plugin)
     .use(admon_plugin)
+    .use(container_plugin, "block", validate=lambda params, _markup:
+         bool(_CONTAINER_NAME_RE.fullmatch(params)), render=_container_render)
     .use(footnote_plugin)
     .use(deflist_plugin)
     .use(tasklists_plugin, enabled=True)
@@ -169,6 +256,10 @@ md = (
     .use(superscript_plugin)
 )
 md.add_render_rule("image", _image_rule)
+# GFM alerts (`> [!NOTE]` etc.), built into markdown-it-py's blockquote rule.
+md.options["alerts"] = True
+# Block attrs must be stripped before the typographer curlifies their quotes.
+md.core.ruler.before("replacements", "block_attrs", _block_attrs)
 md.core.ruler.push("unwrap_lone_figures", _unwrap_lone_figures)
 md.core.ruler.push("tag_task_checkboxes", _tag_task_checkboxes)
 md.core.ruler.push("shorten_autolinks", _shorten_autolinks)

pagerite/themes/corporate/theme.css

@@ -32,11 +32,6 @@
   }
 }
 
-::selection {
-  background: var(--accent);
-  color: #fff;
-}
-
 /* Genuinely large solid brand with a soft blue shadow overlapping the
    artwork — conservative, but unmissable. */
 #brand {

pagerite/themes/nitro/banner.css

@@ -2,12 +2,6 @@
    (inlined by the backend into #page-banner), in neutral dark greys that
    follow the page's color scheme. */
 
-/* Bezier-swept banner with wide orange stripes (inlined SVG), separated
-   from the page by a straight orange blade. */
-#banner {
-  border-bottom: 4px solid var(--accent);
-}
-
 /* Banner artwork dark tones: neutral greys in light mode (retinted to the
    page's violet family by the dark-scheme block below). */
 .nb-base {

pagerite/themes/nitro/theme.css

@@ -63,13 +63,19 @@
 
 ::selection {
   background: var(--accent);
-  color: var(--ink);
+}
+
+/* Any banner used is separated from page by a thick orange line */
+#banner {
+  border-bottom: 4px solid var(--accent);
 }
 
 /* Oversized outlined brand, spilling off the banner edge: orange stroke,
    solid black fill. */
 #brand {
-  font-size: 10rem;
+  /* Scales down proportionally below ~1000px: 10rem at a 62.5rem viewport,
+     shrinking with vmin (smaller of viewport width/height) below that. */
+  font-size: clamp(2.5rem, 16vmin, 10rem);
   line-height: 1.2;
   font-weight: 700;
   letter-spacing: 0.04em;

pagerite/themes/purple/theme.css

@@ -19,11 +19,6 @@
   --font-heading: var(--font-fraunces);
 }
 
-::selection {
-  background: var(--accent2);
-  color: #fff;
-}
-
 /* Oversized tilted brand in the sky→violet gradient. */
 #brand {
   font-size: clamp(3.2rem, 9vw, 7.5rem);

pagerite/themes/summer/theme.css

@@ -57,11 +57,6 @@ body {
   color: var(--text);
 }
 
-::selection {
-  background: var(--sun);
-  color: #3d5223;
-}
-
 /* No separation between banner and page: the frame loses its background,
    border and shadow, and the artwork overflows into the document below,
    masked by a transparency gradient so it cross-fades into the body's fixed