From 7d1fe776c78c2e43586a2411e2ef5d7957ac13ca Mon Sep 17 00:00:00 2001
From: Lee Cattarin <lee.cattarin@gmail.com>
Date: Fri, 20 Feb 2026 08:36:46 -0800
Subject: [PATCH] add related posts and update some styling

---
 _config/filters.js                            | 41 ++++++++++++++++++-
 _includes/layouts/base.njk                    |  2 -
 _includes/layouts/post.njk                    | 13 ++++++
 css/main.css                                  | 15 +++----
 css/nav.css                                   |  4 +-
 css/post.css                                  |  1 -
 src/posts/2026/2026-02-19-eleventy-lessons.md | 16 +++++---
 7 files changed, 73 insertions(+), 19 deletions(-)

diff --git a/_config/filters.js b/_config/filters.js
index 03042e8..4a8f348 100644
--- a/_config/filters.js
+++ b/_config/filters.js
@@ -6,11 +6,50 @@ export default function(eleventyConfig) {
 		return Object.keys(target);
 	});
 
+	/* Exclude all posts with given URLs from a collection list */
+	eleventyConfig.addFilter("excludeFromCollection", function (collection=[], urls=[this.ctx.page.url]) {
+		return collection.filter(post => urls.indexOf(post.url) === -1);
+	});
+
+	/* Filter a collection by a set of tags, returning any that share one or more tags */
+	eleventyConfig.addFilter("filterByTags", function(collection=[], ...requiredTags) {
+		  return collection.filter(post => {
+			return requiredTags.flat().some(tag => post.data.tags.includes(tag));
+		});
+	});
+
+	/* Return n elements from a list */
+	eleventyConfig.addFilter("head", (collection=[], n) => {
+		if(!Array.isArray(collection) || collection.length === 0) {
+			return [];
+		}
+		if( n < 0 ) {
+			return collection.slice(n);
+		}
+
+		return collection.slice(0, n);
+	});
+
+
 	/* For <time> elements */
 	eleventyConfig.addFilter("htmlDateString", (dateObj) => {
 		return DateTime.fromJSDate(dateObj, { zone: "utc" }).toFormat('yyyy-LL-dd');
 	});
 
+	/* What it says on the tin */
+	eleventyConfig.addFilter("randomize", function(array) {
+		// Create a copy of the array to avoid modifying the original
+		let shuffledArray = array.slice();
+
+		// Fisher-Yates shuffle algorithm
+		for (let i = shuffledArray.length - 1; i > 0; i--) {
+				const j = Math.floor(Math.random() * (i + 1));
+				[shuffledArray[i], shuffledArray[j]] = [shuffledArray[j], shuffledArray[i]];
+		}
+
+		return shuffledArray;
+	});
+
 	/* Human-readable dates */
 	eleventyConfig.addFilter("readableDate", (dateObj, format, zone) => {
 		return DateTime.fromJSDate(dateObj, { zone: zone || "utc" })
@@ -22,7 +61,7 @@ export default function(eleventyConfig) {
 		return tags.filter(tag => ["all", "posts", "gallery", "reference", "tagPagination"].indexOf(tag) === -1);
 	});
 
-	/* What it says */
+	/* What it says on the tin */
 	eleventyConfig.addFilter("sortAlphabetically", strings =>
 		(strings || []).sort((b, a) => b.localeCompare(a))
 	);
diff --git a/_includes/layouts/base.njk b/_includes/layouts/base.njk
index f03a97d..d66ada0 100644
--- a/_includes/layouts/base.njk
+++ b/_includes/layouts/base.njk
@@ -41,8 +41,6 @@
 
   <main id="main">
     {{ content | safe }}
-
-    <hr>
   </main>
 
   {% include "footer.njk" %}
diff --git a/_includes/layouts/post.njk b/_includes/layouts/post.njk
index bbd2b70..bd37f4b 100644
--- a/_includes/layouts/post.njk
+++ b/_includes/layouts/post.njk
@@ -3,6 +3,7 @@ layout: base.njk
 ---
 {% css %}{% include "css/post.css" %}{% endcss %}
 {% css %}{% include "css/highlighting.css" %}{% endcss %}
+{% css %}{% include "css/lists.css" %}{% endcss %}
 {% js %}{% include "node_modules/@zachleat/heading-anchors/heading-anchors.js" %}{% endjs %}
 
 <heading-anchors content="<i class='fa-solid fa-anchor'></i>">
@@ -43,4 +44,16 @@ layout: base.njk
   {% set newerTitle = newerPost.data.title %}
   {% set inPost = true %}
   {% include "pagination.njk" %}
+
+  <hr>
+
+  {% set relevantTags = tags | removeBasicTags %}
+  {% set postlist = collections.posts | filterByTags(relevantTags) | excludeFromCollection([page.url, olderHref, newerHref]) | randomize | head(3) %}
+  {% if postlist.length %}
+  <section class="related-posts">
+    <h2>related posts</h2>
+    {% include "postlist.njk" %}
+  </section>
+  {% endif %}
+
 </heading-anchors>
diff --git a/css/main.css b/css/main.css
index e93b70c..05e302a 100644
--- a/css/main.css
+++ b/css/main.css
@@ -49,8 +49,6 @@
 	--color-blue: light-dark(var(--color-blue-dark), var(--color-blue-light));
 	--color-purple: light-dark(var(--color-purple-dark), var(--color-purple-light));
 	--color-grey: light-dark(var(--color-grey-dark), var(--color-grey-light));
-
-	--header-offset: 3.1rem;
 }
 
 /* Base */
@@ -71,7 +69,7 @@ main {
 	width: 60vw;
 	max-width: 1000px;
 	margin: 0 auto;
-	scroll-margin-top: var(--header-offset);
+	scroll-margin-top: 7rem;
 }
 
 @media (max-width: 1050px) {
@@ -90,7 +88,6 @@ main {
 h1, h2, h3, h4, h5, h6 {
 	line-height: 1.25;
 	color: var(--color-teal);
-	scroll-margin-top: var(--header-offset);
 }
 
 h1 {
@@ -99,6 +96,10 @@ h1 {
 	text-align: center;
 }
 
+h2, h3, h4, h5, h6 {
+	scroll-margin-top: 5rem;
+}
+
 h2 {
 	margin-top: 2rem;
 	font-size: 2.2rem;
@@ -260,13 +261,9 @@ time {
 
 /* Horizontal rules */
 hr {
-	color: var(--color-teal);
-	border: .25rem solid var(--color-teal);
+	border: .25rem solid var(--color-pink);
 	margin: 2rem 0;
 }
-hr:last-child {
-	margin-bottom: 0;
-}
 
 /* Used on home, reference, gallery pages */
 .centered {
diff --git a/css/nav.css b/css/nav.css
index f4acb26..aa77be6 100644
--- a/css/nav.css
+++ b/css/nav.css
@@ -3,9 +3,10 @@ header {
 	position: sticky;
 	top: 0;
 	background-color: var(--color-bg);
-	box-shadow: 0 .25rem .15rem var(--color-shadow);
 	padding: .75rem 0;
 	z-index: 10;
+	border-bottom: .5rem solid var(--color-teal);
+	box-shadow: 0 .25rem .15rem var(--color-shadow);
 }
 
 /* Header links, pagination links */
@@ -198,6 +199,7 @@ header li {
 footer {
 	padding: 1rem 0;
 	font-size: .9rem;
+	border-top: .5rem solid var(--color-pink);
 }
 
 footer ul {
diff --git a/css/post.css b/css/post.css
index 2cb3af1..6af12fd 100644
--- a/css/post.css
+++ b/css/post.css
@@ -72,4 +72,3 @@
 	left: .1rem;
 	box-shadow: .05rem .05rem var(--color-shadow);
 }
-
diff --git a/src/posts/2026/2026-02-19-eleventy-lessons.md b/src/posts/2026/2026-02-19-eleventy-lessons.md
index a33fe91..edeb3a0 100644
--- a/src/posts/2026/2026-02-19-eleventy-lessons.md
+++ b/src/posts/2026/2026-02-19-eleventy-lessons.md
@@ -8,7 +8,7 @@ tags:
   - software
 ---
 
-recently I wrote *several* sites using [Eleventy](https://www.11ty.dev/){target="_blank" rel="external"} (4? 5?). Including, over the past few days, this one! That's right, if you're reading this, we're now running on 11ty and hosted by [heckin.technology](https://heckin.technology/){target="_blank" rel="external"}. See ya, GitHub. Won't miss ya.
+recently I wrote *several* sites using [Eleventy](https://www.11ty.dev/){target="_blank" rel="external"} (4? 5?). Including, over the past few days, rewriting this one! That's right, if you're reading this, we're now running on 11ty and hosted by [heckin.technology](https://heckin.technology/){target="_blank" rel="external"}. See ya, GitHub. Won't miss ya.
 
 I've compiled some of the things I've learned in a standalone site: [11ty Lessons](https://inherentlee.codeberg.page/lessons/){target="_blank" rel="external"}.
 
@@ -26,18 +26,19 @@ while that is useful for *this* site, when building another site I wanted to see
 
 I started by referring to [this GitHub issue about related posts](https://github.com/11ty/eleventy/discussions/2534){target="_blank rel="external"}. I had to fix a few errors that arose from the suggested code.
 
-I also wanted to make two changes:
+I also wanted to make three changes:
 
 1. I didn't want to just see posts that shared *all* tags, but rather posts that shared *any* tag
 1. I wanted to randomly add a few posts instead of just getting whatever was first (with a shared tag) in the post order
+1. I wanted to exclude the posts that I could reach with between-post pagination
 
 ### filters.js
 
 after adjusting for those needs, I had the following in `filters.js`:
 
 ```js
-eleventyConfig.addNunjucksFilter("excludeFromCollection", function (collection=[], pageUrl=this.ctx.page.url) {
-  return collection.filter(post => post.url !== pageUrl);
+eleventyConfig.addFilter("excludeFromCollection", function (collection=[], urls=[this.ctx.page.url]) {
+  return collection.filter(post => urls.indexOf(post.url) === -1);
 });
 
 eleventyConfig.addFilter("filterByTags", function(collection=[], ...requiredTags) {
@@ -67,7 +68,12 @@ I used this in my post layout. `filterTagList` comes with the base blog by defau
 {% raw %}
 ```html
 {% set relevantTags = tags | filterTagList %}
-{% set postlist = collections.posts | filterByTags(relevantTags) | excludeFromCollection(page.url) | randomize | head(2) %}
+
+{% set olderPost = collections.posts | getPreviousCollectionItem %}
+{% set newerPost = collections.posts | getNextCollectionItem %}
+{% set urlsToExclude = [page.url, olderPost.url, newerPost.url]}
+
+{% set postlist = collections.posts | filterByTags(relevantTags) | excludeFromCollection(urlsToExclude) | randomize | head(3) %}
 {% if postlist.length %}
 <section class="related-posts">
 	<h2>related posts</h2>