diff --git a/docs/_layouts/default.html b/docs/_layouts/default.html
index 18305f8..35f64ae 100644
--- a/docs/_layouts/default.html
+++ b/docs/_layouts/default.html
@@ -6,6 +6,8 @@
   <meta name="theme-color" content="#101217">
   {% seo %}
   {% feed_meta %}
+  <link rel="icon" type="image/svg+xml" href="{{ '/assets/mark/psi.svg' | relative_url }}">
+  <link rel="apple-touch-icon" href="{{ '/assets/mark/psi-180.png' | relative_url }}">
   <link rel="stylesheet" href="{{ '/assets/notebook.css' | relative_url }}">
   {% if page.profiles %}<script defer src="{{ '/assets/profile-comparison.js' | relative_url }}"></script>{% endif %}
   {% if page.mesh_band %}<script defer src="{{ '/assets/mesh-band.js' | relative_url }}"></script>{% endif %}
@@ -17,7 +19,12 @@
 <body>
   <a class="skip" href="#content">Skip to content</a>
   <header class="site-header wrap">
-    <a class="wordmark" href="{{ '/' | relative_url }}"><span class="mark" aria-hidden="true">∿</span> {{ site.title }}</a>
+    <a class="wordmark" href="{{ '/' | relative_url }}"><svg class="mark" viewBox="0 0 100 100" aria-hidden="true">
+  <path d="M 50 26.06 L 50 69.74 Z" fill="none" stroke="#edf0f5" stroke-width="7.14" stroke-linecap="square" stroke-linejoin="miter" stroke-miterlimit="4"/>
+  <path d="M 50 38.24 L 20.6 18.5 L 50 44.12 Z" fill="none" stroke="#edf0f5" stroke-width="7.14" stroke-linecap="square" stroke-linejoin="miter" stroke-miterlimit="4"/>
+  <path d="M 50 38.24 L 79.4 18.5 L 50 44.12 Z" fill="none" stroke="#edf0f5" stroke-width="7.14" stroke-linecap="square" stroke-linejoin="miter" stroke-miterlimit="4"/>
+  <path d="M 50 69.74 L 50 84.02 Z" fill="none" stroke="#91dbba" stroke-width="7.14" stroke-linecap="square" stroke-linejoin="miter" stroke-miterlimit="4"/>
+</svg> {{ site.title }}</a>
     <nav aria-label="Main navigation">
       {% for item in site.navigation %}<a href="{% if item.external %}{{ item.url }}{% else %}{{ item.url | relative_url }}{% endif %}" {% if page.url == item.url %}aria-current="page"{% endif %}>{{ item.title }}</a>{% endfor %}
     </nav>
diff --git a/docs/assets/mark/psi-180.png b/docs/assets/mark/psi-180.png
new file mode 100644
index 0000000..39fb7c4
Binary files /dev/null and b/docs/assets/mark/psi-180.png differ
diff --git a/docs/assets/mark/psi.svg b/docs/assets/mark/psi.svg
new file mode 100644
index 0000000..6f13363
--- /dev/null
+++ b/docs/assets/mark/psi.svg
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Generated by assets/mark/render_mark.py from assets/mark/psi.json.
+     Do not edit by hand: run `python assets/mark/render_mark.py` instead. -->
+<!-- Unit square mapped to the viewBox as v' = 8 + 84 v.
+     Stroke 0.085 unit-square units = 7.14 viewBox units.
+     Each part is a closed polygon stroked in its palette colour
+     (#edf0f5 = ink, #91dbba = accent). -->
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <title>psi monogram</title>
+  <path d="M 50 26.06 L 50 69.74 Z" fill="none" stroke="#edf0f5" stroke-width="7.14" stroke-linecap="square" stroke-linejoin="miter" stroke-miterlimit="4"/>
+  <path d="M 50 38.24 L 20.6 18.5 L 50 44.12 Z" fill="none" stroke="#edf0f5" stroke-width="7.14" stroke-linecap="square" stroke-linejoin="miter" stroke-miterlimit="4"/>
+  <path d="M 50 38.24 L 79.4 18.5 L 50 44.12 Z" fill="none" stroke="#edf0f5" stroke-width="7.14" stroke-linecap="square" stroke-linejoin="miter" stroke-miterlimit="4"/>
+  <path d="M 50 69.74 L 50 84.02 Z" fill="none" stroke="#91dbba" stroke-width="7.14" stroke-linecap="square" stroke-linejoin="miter" stroke-miterlimit="4"/>
+</svg>
diff --git a/docs/assets/notebook.css b/docs/assets/notebook.css
index 110c80e..57f4a77 100644
--- a/docs/assets/notebook.css
+++ b/docs/assets/notebook.css
@@ -24,7 +24,7 @@ a:focus-visible, summary:focus-visible, [tabindex]:focus-visible { outline: 2px
 .wrap { width: min(1120px, calc(100% - 64px)); margin-inline: auto; }
 .site-header { display: flex; align-items: center; justify-content: space-between; gap: 24px; padding-block: 23px; border-bottom: 1px solid var(--rule); }
 .wordmark { display: flex; align-items: center; gap: 10px; color: var(--ink); font-size: 17px; font-weight: 650; letter-spacing: -.4px; text-decoration: none; }
-.mark { display: inline-grid; place-items: center; width: 27px; height: 27px; border: 1px solid #657dab; border-radius: 7px; color: var(--accent); font-size: 23px; line-height: 1; }
+.mark { display: inline-grid; place-items: center; width: 27px; height: 27px; border: 1px solid #657dab; border-radius: 7px; color: var(--accent); }
 nav { display: flex; gap: 22px; flex-wrap: wrap; font-size: 12px; }
 nav a { color: var(--muted); text-decoration: none; }
 nav a:hover, nav [aria-current] { color: var(--ink); }
