From cb8c54e8488806febb2d2204e3ae6a4687386c87 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Tue, 20 Oct 2026 12:53:34 +0000
Subject: [PATCH 1/2] Seasonal themes: a themed animation for every week, plus
 events

Every week of the year gets a theme from config.toml [seasons]: a few
themed emoji drift down (or float up) behind the content on every page,
and the topographic lines take the theme's two colours. October is
spooky, December has the winter holidays, and dated events take over
while they run (All Things Open, Oct 19-21 2026).

The theme is picked in the browser from today's date, so it changes with
no redeploy. CSS animations only, never in the way of a tap, and hidden
for reduced motion and data saving. The config is checked at build time
like the other sections (emoji, colours, names and dates), with tests.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nginuw5wmUjUSkmQB1J3pS
---
 .gitignore                             |   1 +
 README.md                              |  13 +-
 components/SeasonalParticles.vue       | 100 +++++++
 components/TopoBackground.vue          |   7 +-
 composables/useSeason.js               |  15 ++
 config.toml                            | 350 ++++++++++++++++++++++++-
 layouts/default.vue                    |   1 +
 package.json                           |   5 +-
 scripts/build-seasons.mjs              |  21 ++
 tests/app/seasons.test.mjs             |  72 +++++
 tests/security/payloads.mjs            |  14 +
 tests/security/seasons-config.test.mjs |  60 +++++
 utils/seasons.mjs                      | 156 +++++++++++
 13 files changed, 809 insertions(+), 6 deletions(-)
 create mode 100644 components/SeasonalParticles.vue
 create mode 100644 composables/useSeason.js
 create mode 100644 scripts/build-seasons.mjs
 create mode 100644 tests/app/seasons.test.mjs
 create mode 100644 tests/security/seasons-config.test.mjs
 create mode 100644 utils/seasons.mjs

diff --git a/.gitignore b/.gitignore
index 21a306c0..61ec8f60 100644
--- a/.gitignore
+++ b/.gitignore
@@ -97,6 +97,7 @@ netlify/lib/access.mjs
 data/projects.generated.mjs
 data/background.generated.mjs
 data/coinBubble.generated.mjs
+data/seasons.generated.mjs
 data/credits.generated.json
 data/contributions.generated.json
 content/bio/github-readme.generated.md
diff --git a/README.md b/README.md
index d30ee6e9..db8fa5f7 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,7 @@ These run before `npm run dev`, `npm test` and the builds. The files they write
 - `build:access`: the sign-in allow-list, from `.github/CODEOWNERS` and `config.toml` → `netlify/lib/access.mjs`.
 - `build:projects`: the Projects settings in `config.toml` → `data/projects.generated.mjs`.
 - `build:background`: the topographic background settings in `config.toml` → `data/background.generated.mjs`.
+- `build:seasons`: the seasonal themes in `config.toml` → `data/seasons.generated.mjs`.
 - `build:credits`: the open-source credits page (`/credits`) → `data/credits.generated.json`. It credits every package in `package.json` (plus the libraries bundled with Nuxt and its Tailwind module, `INCLUDED` in `utils/credits.mjs`) at the version in `package-lock.json`, with the license, copyright line and GitHub link from `node_modules`. The page then refreshes from the `/api/credits` Netlify function, which reads the project's `package.json` and `package-lock.json` from GitHub (`main`, so merged dependency changes show up without a deploy; it falls back to the deployed copies) and each package's details from the npm registry and jsDelivr (cached by Netlify's CDN for a day). Nothing to update by hand when dependencies change.
 - `sync:contributions`: the GitHub contribution calendar for the Projects page → `data/contributions.generated.json`.
 - `sync:readme`: the GitHub profile README for the Bio page → `content/bio/github-readme.generated.md`.
@@ -51,7 +52,7 @@ Non-fork repos show automatically. In `config.toml`, under `[projects]`:
 - `featured` and `hackathon`: tags for repos that are already shown.
 
 ## Topographic background
-Faint purple-to-green contour lines sit behind every page and draw in as visitors stay. They're built in the browser at the screen's size, in a Web Worker (`workers/topo.worker.mjs`, `utils/topo.mjs`). Tune them in `config.toml` under `[background]`; the build fails on a value out of range:
+Faint purple-to-green contour lines (in the season's colours while a seasonal theme is on, see below) sit behind every page and draw in as visitors stay. They're built in the browser at the screen's size, in a Web Worker (`workers/topo.worker.mjs`, `utils/topo.mjs`). Tune them in `config.toml` under `[background]`; the build fails on a value out of range:
 - `enabled`: `true` or `false`.
 - `data_saver`: what to do when the browser asks to save data. That's detected automatically: Data Saver or Lite mode (`navigator.connection.saveData`), the `prefers-reduced-data` media query, or a 2G or slower connection.
   - `"sparse"` (the default): a lighter pattern with half the contours, larger hills, no trails and a coarser grid, about a quarter of the size.
@@ -63,6 +64,16 @@ Faint purple-to-green contour lines sit behind every page and draw in as visitor
 - `trails` (0–6): dashed trails that fade in at the end.
 - `draw_seconds` (0–600): time on the page to draw everything. `0` shows it all at once. Reduced-motion settings also show it all at once.
 
+## Seasonal themes
+Every week of the year has a theme: a few themed emoji drift down (or float up) over the background on every page, and the topographic lines take the theme's two colours. October is spooky (Hacktoberfest, pumpkins, bats, Halloween), December has the winter holidays, and so on. Dated events take over while they run, like All Things Open in Raleigh with laptops, Linux penguins and Raleigh's acorns.
+- The themes live in `config.toml` under `[seasons]`, checked by `utils/seasons.mjs`; the build fails on a bad value.
+  - `enabled`: `true` or `false`.
+  - `particles` (0–40): how many emoji at once. Phones show at most 8.
+  - `[[seasons.week]]`: one per week, in order from `from = "01-01"`. Each runs until the next one starts. Each has a `name`, up to 8 `emoji`, two `colors` (`"#rrggbb"`) and a `motion` (`"fall"`, the default, or `"rise"`).
+  - `[[seasons.event]]`: the same, with `from` and `to` dates (like `2026-10-19`). Events take over from the weekly theme for those days.
+- The theme is picked in the visitor's browser from today's date (Eastern time), so it changes on its own with no redeploy (`composables/useSeason.js`).
+- The emoji are CSS animations only (`components/SeasonalParticles.vue`), behind the page content and never in the way of a tap. They're hidden for visitors who prefer reduced motion or are saving data; the colours still change.
+
 ## Coin face (home page)
 The coin opens on the Bitmoji. Each time a flip lands heads up, the face shows the next photo, alternating between the GitHub avatar and the hanselwei.link Gravatar (`utils/coinFaces.mjs`). The pull-down reset brings the Bitmoji back. A photo that can't load is skipped, so the coin never goes blank.
 
diff --git a/components/SeasonalParticles.vue b/components/SeasonalParticles.vue
new file mode 100644
index 00000000..eac3c6a0
--- /dev/null
+++ b/components/SeasonalParticles.vue
@@ -0,0 +1,100 @@
+<template>
+  <div v-if="particles.length" :class="['season', `season--${theme.motion}`]" aria-hidden="true">
+    <span
+      v-for="p in particles"
+      :key="p.id"
+      class="season__particle"
+      :style="{
+        left: `${p.x}%`,
+        '--size': `${p.size}rem`,
+        '--duration': `${p.duration}s`,
+        '--delay': `${p.delay}s`,
+        '--sway': `${p.sway}s`,
+        '--spin': `${p.spin}deg`
+      }"
+    ><span class="season__emoji">{{ p.emoji }}</span></span>
+  </div>
+</template>
+
+<script setup>
+// This week's theme (config.toml [seasons]): a few themed emoji drifting down (or floating up)
+// over the background on every page, behind the content and never in the way of a tap. Off for
+// visitors who prefer reduced motion or are saving data. CSS animations only, so nothing runs
+// on the main thread once they're placed.
+import { particleLayout } from '~/utils/seasons.mjs'
+import { wantsLessData } from '~/utils/background.mjs'
+import { seasonParticles } from '~/composables/useSeason.js'
+
+const theme = useSeason()
+const particles = ref([])
+
+onMounted(() => {
+  const reducedMotion = window.matchMedia('(prefers-reduced-motion: reduce)').matches
+  const lessData = wantsLessData({
+    saveData: navigator.connection?.saveData,
+    effectiveType: navigator.connection?.effectiveType,
+    reducedData: window.matchMedia('(prefers-reduced-data: reduce)').matches
+  })
+  if (reducedMotion || lessData) return
+  // useSeason picks the theme in its own onMounted, which has run by now
+  particles.value = particleLayout(theme.value, seasonParticles)
+})
+</script>
+
+<style scoped>
+/* Over the topographic lines, under everything else (see TopoBackground.vue) */
+.season {
+  position: fixed;
+  inset: 0;
+  z-index: -1;
+  overflow: hidden;
+  pointer-events: none;
+}
+
+.season__particle {
+  position: absolute;
+  top: 0;
+  font-size: var(--size);
+  line-height: 1;
+  opacity: 0.55;
+  will-change: transform;
+  animation: season-fall var(--duration) linear var(--delay) infinite;
+}
+
+.season--rise .season__particle {
+  animation-name: season-rise;
+}
+
+.season__emoji {
+  display: inline-block;
+  animation: season-sway var(--sway) ease-in-out infinite alternate;
+}
+
+/* Phones: fewer at once */
+@media (max-width: 640px) {
+  .season__particle:nth-child(n + 9) {
+    display: none;
+  }
+}
+
+@keyframes season-fall {
+  from { transform: translateY(-10vh) rotate(0); }
+  to { transform: translateY(110vh) rotate(var(--spin)); }
+}
+
+@keyframes season-rise {
+  from { transform: translateY(110vh) rotate(0); }
+  to { transform: translateY(-10vh) rotate(var(--spin)); }
+}
+
+@keyframes season-sway {
+  from { transform: translateX(-18px); }
+  to { transform: translateX(18px); }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .season {
+    display: none;
+  }
+}
+</style>
diff --git a/components/TopoBackground.vue b/components/TopoBackground.vue
index 8eafaf71..f147357b 100644
--- a/components/TopoBackground.vue
+++ b/components/TopoBackground.vue
@@ -10,8 +10,8 @@
     <template v-if="topo">
       <defs>
         <linearGradient id="topo-gradient" gradientUnits="userSpaceOnUse" x1="0" y1="0" :x2="topo.width" :y2="topo.height">
-          <stop offset="0" stop-color="#c084fc" />
-          <stop offset="1" stop-color="#41b883" />
+          <stop offset="0" :stop-color="season?.colors[0] ?? '#c084fc'" />
+          <stop offset="1" :stop-color="season?.colors[1] ?? '#41b883'" />
         </linearGradient>
       </defs>
       <path
@@ -41,6 +41,9 @@ import { topoOptions, wantsLessData } from '~/utils/background.mjs'
 // config.toml [background], checked at build time (scripts/build-background.mjs)
 import settings from '~/data/background.generated.mjs'
 
+// This week's theme (config.toml [seasons]) colours the lines; purple to green otherwise
+const season = useSeason()
+
 // The lines draw in as the visitor stays: the whole pattern takes this long with the tab visible
 const FULL_DRAW_MS = settings.drawSeconds * 1000
 const PAINT_EVERY_MS = 100 // the draw is slow, so ten updates a second is plenty
diff --git a/composables/useSeason.js b/composables/useSeason.js
new file mode 100644
index 00000000..ecf73f0e
--- /dev/null
+++ b/composables/useSeason.js
@@ -0,0 +1,15 @@
+// Today's seasonal theme (utils/seasons.mjs, config.toml [seasons]), or null. Picked in the
+// browser once the page is up: the prerendered page has no theme, so it fits any day.
+import settings from '~/data/seasons.generated.mjs'
+import { themeFor } from '~/utils/seasons.mjs'
+import { dayIn } from '~/utils/coinBubble.mjs'
+
+export const useSeason = () => {
+  const theme = useState('season:theme', () => null)
+  onMounted(() => {
+    theme.value ??= themeFor(settings, dayIn(new Date()))
+  })
+  return theme
+}
+
+export const seasonParticles = settings.particles
diff --git a/config.toml b/config.toml
index 5d814b46..dc2f9738 100644
--- a/config.toml
+++ b/config.toml
@@ -22,7 +22,8 @@ featured = []
 hackathon = ["HackNC2019"]
 
 [background]
-# The faint topographic lines behind every page (purple-to-green, drawing in as visitors stay).
+# The faint topographic lines behind every page (purple-to-green, or the season's colours from
+# [seasons] below, drawing in as visitors stay).
 # Leave a setting out to use its default. The build fails on a value out of range.
 # More contours or smaller features mean more drawing data on big screens (about 0.3 MB at
 # these values on a 2560px-wide screen, up to about 1.6 MB at 60 contours and 80px features).
@@ -51,3 +52,350 @@ qr = "https://hanselwei.dev"  # where the QR on the coin's tails side points (ht
 # Also during the event: the home page title, and a line at the top of the footer on every page
 home_title = "Hansel Wei, Senior Software Engineer"  # up to 80 characters
 footer_code = "WKZBHNUJRETD"  # up to 40 characters
+
+[seasons]
+# Seasonal themes on every page: a few themed emoji drifting over the background, and the
+# topographic lines in the theme's two colours. Picked in the visitor's browser from today's
+# date (Eastern time), so the themes change on their own with no redeploy. Hidden for visitors
+# who prefer reduced motion or are saving data. `enabled = false` turns it all off.
+enabled = true
+particles = 12  # how many emoji at once (0–40; phones show at most 8)
+
+# A theme for every week of the year, in order from Jan 1. Each runs from its `from` day
+# (month-day) until the next one starts. emoji: up to 8; colors: the topographic lines'
+# gradient; motion: "fall" (drift down) or "rise" (float up).
+
+[[seasons.week]]
+from = "01-01"
+name = "New Year"
+emoji = ["🎆", "🥂", "🎉", "✨"]
+colors = ["#facc15", "#a855f7"]
+motion = "rise"
+
+[[seasons.week]]
+from = "01-08"
+name = "Snow days"
+emoji = ["❄️", "🌨️", "⛄"]
+colors = ["#93c5fd", "#e0f2fe"]
+
+[[seasons.week]]
+from = "01-15"
+name = "Dream big (MLK Day)"
+emoji = ["🕊️", "💜", "✨"]
+colors = ["#a78bfa", "#38bdf8"]
+motion = "rise"
+
+[[seasons.week]]
+from = "01-22"
+name = "Lunar New Year"
+emoji = ["🧧", "🏮", "🐉", "🎆"]
+colors = ["#ef4444", "#facc15"]
+
+[[seasons.week]]
+from = "01-29"
+name = "Cozy winter"
+emoji = ["☕", "🧣", "❄️"]
+colors = ["#d6a77a", "#93c5fd"]
+
+[[seasons.week]]
+from = "02-05"
+name = "Big game"
+emoji = ["🏈", "🏟️", "🎉"]
+colors = ["#16a34a", "#f59e0b"]
+
+[[seasons.week]]
+from = "02-12"
+name = "Valentine's"
+emoji = ["💘", "💝", "🌹", "💌"]
+colors = ["#f43f5e", "#f9a8d4"]
+motion = "rise"
+
+[[seasons.week]]
+from = "02-19"
+name = "Winter thaw"
+emoji = ["💧", "🌱", "❄️"]
+colors = ["#7dd3fc", "#86efac"]
+
+[[seasons.week]]
+from = "02-26"
+name = "Leap into March"
+emoji = ["🐸", "🌱", "🍃"]
+colors = ["#22c55e", "#a3e635"]
+
+[[seasons.week]]
+from = "03-05"
+name = "Kite winds"
+emoji = ["🪁", "🌬️", "🍃"]
+colors = ["#38bdf8", "#facc15"]
+motion = "rise"
+
+[[seasons.week]]
+from = "03-12"
+name = "Pi Day and St Patrick's"
+emoji = ["🥧", "☘️", "🍀", "🌈"]
+colors = ["#22c55e", "#facc15"]
+
+[[seasons.week]]
+from = "03-19"
+name = "Spring equinox"
+emoji = ["🌷", "🌸", "🐣"]
+colors = ["#f9a8d4", "#86efac"]
+
+[[seasons.week]]
+from = "03-26"
+name = "Bracket season"
+emoji = ["🏀", "🏆"]
+colors = ["#f97316", "#3b82f6"]
+
+[[seasons.week]]
+from = "04-02"
+name = "April showers"
+emoji = ["☔", "🌧️", "🐸"]
+colors = ["#60a5fa", "#a3e635"]
+
+[[seasons.week]]
+from = "04-09"
+name = "Cherry blossoms"
+emoji = ["🌸", "🌺", "🦋"]
+colors = ["#f9a8d4", "#c084fc"]
+
+[[seasons.week]]
+from = "04-16"
+name = "Earth Day"
+emoji = ["🌍", "🌱", "♻️", "🌳"]
+colors = ["#22c55e", "#0ea5e9"]
+motion = "rise"
+
+[[seasons.week]]
+from = "04-23"
+name = "Spring bunnies"
+emoji = ["🐰", "🥚", "🐣", "🌷"]
+colors = ["#fde68a", "#c4b5fd"]
+
+[[seasons.week]]
+from = "04-30"
+name = "May the 4th"
+emoji = ["⭐", "🚀", "🌌", "🪐"]
+colors = ["#facc15", "#60a5fa"]
+motion = "rise"
+
+[[seasons.week]]
+from = "05-07"
+name = "Mother's Day"
+emoji = ["💐", "🌷", "💖"]
+colors = ["#f472b6", "#fda4af"]
+
+[[seasons.week]]
+from = "05-14"
+name = "Bees and blooms"
+emoji = ["🐝", "🌼", "🌻"]
+colors = ["#facc15", "#84cc16"]
+motion = "rise"
+
+[[seasons.week]]
+from = "05-21"
+name = "Cookout"
+emoji = ["🌭", "🍔", "🍉"]
+colors = ["#ef4444", "#f59e0b"]
+
+[[seasons.week]]
+from = "05-28"
+name = "Pride begins"
+emoji = ["🏳️‍🌈", "🌈", "✨"]
+colors = ["#ec4899", "#3b82f6"]
+motion = "rise"
+
+[[seasons.week]]
+from = "06-04"
+name = "Pride"
+emoji = ["🏳️‍🌈", "💖", "🌈", "✨"]
+colors = ["#f43f5e", "#8b5cf6"]
+motion = "rise"
+
+[[seasons.week]]
+from = "06-11"
+name = "Road trip"
+emoji = ["🚗", "🗺️", "☀️"]
+colors = ["#f59e0b", "#0ea5e9"]
+
+[[seasons.week]]
+from = "06-18"
+name = "Summer solstice"
+emoji = ["☀️", "🌻", "😎"]
+colors = ["#facc15", "#fb923c"]
+
+[[seasons.week]]
+from = "06-25"
+name = "Beach days"
+emoji = ["🏖️", "🌊", "🐚", "🦀"]
+colors = ["#38bdf8", "#fde68a"]
+
+[[seasons.week]]
+from = "07-02"
+name = "Fourth of July"
+emoji = ["🎆", "🎇", "🇺🇸", "⭐"]
+colors = ["#ef4444", "#3b82f6"]
+motion = "rise"
+
+[[seasons.week]]
+from = "07-09"
+name = "Camping"
+emoji = ["⛺", "🔥", "🌲", "🌙"]
+colors = ["#16a34a", "#f97316"]
+motion = "rise"
+
+[[seasons.week]]
+from = "07-16"
+name = "Ice cream"
+emoji = ["🍦", "🍉", "🍧"]
+colors = ["#f9a8d4", "#86efac"]
+
+[[seasons.week]]
+from = "07-23"
+name = "Paddle season"
+emoji = ["🛶", "🌊", "🐢"]
+colors = ["#0ea5e9", "#14b8a6"]
+
+[[seasons.week]]
+from = "07-30"
+name = "Trail time"
+emoji = ["⛰️", "🥾", "🌲", "🦌"]
+colors = ["#65a30d", "#a16207"]
+
+[[seasons.week]]
+from = "08-06"
+name = "Perseid meteors"
+emoji = ["🌠", "✨", "🔭"]
+colors = ["#818cf8", "#fde047"]
+
+[[seasons.week]]
+from = "08-13"
+name = "Shark Week"
+emoji = ["🦈", "🌊", "🐟"]
+colors = ["#0284c7", "#64748b"]
+
+[[seasons.week]]
+from = "08-20"
+name = "Back to school"
+emoji = ["📚", "✏️", "🎒", "🍎"]
+colors = ["#ef4444", "#facc15"]
+
+[[seasons.week]]
+from = "08-27"
+name = "Late summer"
+emoji = ["🌻", "🐝", "🍑"]
+colors = ["#f59e0b", "#84cc16"]
+motion = "rise"
+
+[[seasons.week]]
+from = "09-03"
+name = "Labor Day"
+emoji = ["🛠️", "🍔", "🎉"]
+colors = ["#3b82f6", "#ef4444"]
+
+[[seasons.week]]
+from = "09-10"
+name = "Programmers' Day"
+emoji = ["💻", "⌨️", "🐛", "☕"]
+colors = ["#7cfc00", "#22d3ee"]
+
+[[seasons.week]]
+from = "09-17"
+name = "Talk Like a Pirate"
+emoji = ["🏴‍☠️", "🦜", "⚓", "💰"]
+colors = ["#a16207", "#0ea5e9"]
+
+[[seasons.week]]
+from = "09-24"
+name = "First days of fall"
+emoji = ["🍂", "🍁", "🍎"]
+colors = ["#f97316", "#b45309"]
+
+[[seasons.week]]
+from = "10-01"
+name = "Hacktoberfest"
+emoji = ["💻", "🎃", "🌱", "🐙"]
+colors = ["#a855f7", "#7cfc00"]
+
+[[seasons.week]]
+from = "10-08"
+name = "Pumpkin patch"
+emoji = ["🎃", "🍂", "🌽"]
+colors = ["#f97316", "#facc15"]
+
+[[seasons.week]]
+from = "10-15"
+name = "Spooky season"
+emoji = ["👻", "🦇", "🕸️", "🎃"]
+colors = ["#f97316", "#8b5cf6"]
+motion = "rise"
+
+[[seasons.week]]
+from = "10-22"
+name = "Spookier"
+emoji = ["🦇", "🕷️", "🕸️", "💀"]
+colors = ["#7c3aed", "#f97316"]
+
+[[seasons.week]]
+from = "10-29"
+name = "Halloween and Día de Muertos"
+emoji = ["🎃", "👻", "🦇", "🍬", "💀"]
+colors = ["#f97316", "#a855f7"]
+motion = "rise"
+
+[[seasons.week]]
+from = "11-05"
+name = "Falling leaves"
+emoji = ["🍁", "🍂", "🍃"]
+colors = ["#ea580c", "#ca8a04"]
+
+[[seasons.week]]
+from = "11-12"
+name = "Sweater weather"
+emoji = ["🧣", "☕", "🍂"]
+colors = ["#b45309", "#fb923c"]
+
+[[seasons.week]]
+from = "11-19"
+name = "Harvest"
+emoji = ["🦃", "🥧", "🌽", "🍂"]
+colors = ["#d97706", "#92400e"]
+
+[[seasons.week]]
+from = "11-26"
+name = "Thanksgiving"
+emoji = ["🦃", "🥧", "🍁"]
+colors = ["#ea580c", "#a16207"]
+
+[[seasons.week]]
+from = "12-03"
+name = "First snow"
+emoji = ["❄️", "⛄", "🌨️"]
+colors = ["#bae6fd", "#e0e7ff"]
+
+[[seasons.week]]
+from = "12-10"
+name = "Holiday lights"
+emoji = ["🎄", "🕎", "✨", "🎁"]
+colors = ["#22c55e", "#ef4444"]
+
+[[seasons.week]]
+from = "12-17"
+name = "Holidays"
+emoji = ["🎄", "🎁", "⛄", "🍪"]
+colors = ["#16a34a", "#dc2626"]
+
+[[seasons.week]]
+from = "12-24"
+name = "Holidays and New Year's Eve"
+emoji = ["🎄", "🎁", "🎉", "✨"]
+colors = ["#facc15", "#ef4444"]
+
+# Events take over from the weekly theme from `from` through `to` (dates, Eastern time).
+[[seasons.event]]
+name = "All Things Open"
+from = 2026-10-19
+to = 2026-10-21  # All Things Open 2026, Raleigh (October 19–20), plus a day of cooldown
+emoji = ["💻", "🐧", "🌰", "🎤", "⭐", "🔓"]  # 🌰 Raleigh is the City of Oaks
+colors = ["#f97316", "#22d3ee"]
+motion = "rise"
diff --git a/layouts/default.vue b/layouts/default.vue
index e5f3fb38..80048db5 100644
--- a/layouts/default.vue
+++ b/layouts/default.vue
@@ -1,6 +1,7 @@
 <template>
   <div class="app-shell">
     <TopoBackground />
+    <SeasonalParticles />
     <AppNav />
     <PullToRefresh />
     <slot />
diff --git a/package.json b/package.json
index abe312d7..791bf7d4 100644
--- a/package.json
+++ b/package.json
@@ -12,11 +12,12 @@
     "build:background": "node scripts/build-background.mjs",
     "build:credits": "node scripts/build-credits.mjs",
     "build:coin-bubble": "node scripts/build-coin-bubble.mjs",
+    "build:seasons": "node scripts/build-seasons.mjs",
     "sync:contributions": "node scripts/sync-contributions.mjs",
     "sync:readme": "node scripts/sync-readme.mjs",
-    "pretest": "npm run build:access && npm run build:projects && npm run build:background && npm run build:coin-bubble && npm run build:credits && npm run sync:contributions && npm run sync:readme",
+    "pretest": "npm run build:access && npm run build:projects && npm run build:background && npm run build:coin-bubble && npm run build:seasons && npm run build:credits && npm run sync:contributions && npm run sync:readme",
     "test": "node --test \"tests/**/*.test.mjs\"",
-    "predev": "npm run build:access && npm run build:projects && npm run build:background && npm run build:coin-bubble && npm run build:credits && npm run sync:contributions && npm run sync:readme",
+    "predev": "npm run build:access && npm run build:projects && npm run build:background && npm run build:coin-bubble && npm run build:seasons && npm run build:credits && npm run sync:contributions && npm run sync:readme",
     "prebuild": "npm test && npm run sync:devto",
     "build": "nuxt build",
     "start": "nuxt start",
diff --git a/scripts/build-seasons.mjs b/scripts/build-seasons.mjs
new file mode 100644
index 00000000..3cf6818a
--- /dev/null
+++ b/scripts/build-seasons.mjs
@@ -0,0 +1,21 @@
+// Writes data/seasons.generated.mjs from config.toml [seasons] before every build, and fails the
+// build on a bad setting (same as the other config sections).
+import { readFile, writeFile } from 'node:fs/promises'
+import { parse } from 'smol-toml'
+import { buildSeasonsConfig, seasonsModule, themeFor } from '../utils/seasons.mjs'
+import { dayIn } from '../utils/coinBubble.mjs'
+
+const root = new URL('../', import.meta.url)
+const toml = parse((await readFile(new URL('config.toml', root), 'utf8').catch(() => '')) || '')
+const { config, problems } = buildSeasonsConfig(toml)
+
+if (problems.length) {
+  console.error(`[build-seasons] Can't build the seasons config:\n  ${problems.join('\n  ')}`)
+  process.exit(1)
+}
+
+await writeFile(new URL('data/seasons.generated.mjs', root), seasonsModule(config))
+const today = themeFor(config, dayIn(new Date()))
+console.log(
+  `[build-seasons] ${config.enabled ? `${config.weeks.length} weekly themes, ${config.events.length} event(s); today: ${today?.name ?? 'none'}` : 'off'}`
+)
diff --git a/tests/app/seasons.test.mjs b/tests/app/seasons.test.mjs
new file mode 100644
index 00000000..7b746641
--- /dev/null
+++ b/tests/app/seasons.test.mjs
@@ -0,0 +1,72 @@
+// Seasonal themes (config.toml [seasons]): a theme for every week of the year, dated events
+// taking over while they run, and the drifting emoji's layout.
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { readFile } from 'node:fs/promises'
+import { parse } from 'smol-toml'
+import { buildSeasonsConfig, monthDay, particleLayout, themeFor } from '../../utils/seasons.mjs'
+
+const toml = parse(await readFile(new URL('../../config.toml', import.meta.url), 'utf8'))
+const { config, problems } = buildSeasonsConfig(toml)
+
+test("the site's config.toml [seasons] builds", () => {
+  assert.deepEqual(problems, [])
+  assert.equal(config.weeks.length, 52)
+})
+
+test('every day of the year has a theme, leap days included', () => {
+  for (const year of [2026, 2028]) {
+    for (let d = new Date(Date.UTC(year, 0, 1)); d.getUTCFullYear() === year; d.setUTCDate(d.getUTCDate() + 1)) {
+      const day = d.toISOString().slice(0, 10)
+      assert.ok(themeFor(config, day), day)
+    }
+  }
+  assert.equal(themeFor(config, '2028-02-29'), themeFor(config, '2028-02-28'))
+})
+
+test('October is spooky, and All Things Open takes over during the event', () => {
+  assert.match(themeFor(config, '2026-10-31').name, /Halloween/)
+  assert.ok(themeFor(config, '2026-10-31').emoji.includes('🎃'))
+  assert.match(themeFor(config, '2026-10-16').name, /Spooky/)
+  for (const day of ['2026-10-19', '2026-10-20', '2026-10-21']) assert.equal(themeFor(config, day).name, 'All Things Open')
+  assert.notEqual(themeFor(config, '2026-10-22').name, 'All Things Open')
+  assert.notEqual(themeFor(config, '2027-10-20').name, 'All Things Open') // dated: one year only
+})
+
+test('a few holidays land in their week', () => {
+  assert.match(themeFor(config, '2026-01-01').name, /New Year/)
+  assert.match(themeFor(config, '2026-02-14').name, /Valentine/)
+  assert.match(themeFor(config, '2026-03-17').name, /Patrick/)
+  assert.match(themeFor(config, '2026-07-04').name, /Fourth of July/)
+  assert.match(themeFor(config, '2026-12-25').name, /Holidays/)
+  assert.match(themeFor(config, '2026-12-31').name, /New Year's Eve/)
+})
+
+test('weeks must start on Jan 1 and run in order', () => {
+  const week = from => ({ from, name: 'x', emoji: ['⭐'], colors: ['#ffffff', '#000000'] })
+  assert.ok(buildSeasonsConfig({ seasons: { week: [week('01-08')] } }).problems.length)
+  assert.ok(buildSeasonsConfig({ seasons: { week: [week('01-01'), week('03-01'), week('02-01')] } }).problems.length)
+  assert.deepEqual(buildSeasonsConfig({ seasons: { enabled: true, week: [week('01-01'), week('06-01')] } }).problems, [])
+})
+
+test('off, or no date, means no theme', () => {
+  assert.equal(themeFor({ ...config, enabled: false }, '2026-10-31'), null)
+  assert.equal(themeFor(config, undefined), null)
+  assert.equal(monthDay('02-29'), null)
+  assert.equal(monthDay('12-31'), '12-31')
+})
+
+test('particles cycle through the emoji and stay on screen', () => {
+  const theme = themeFor(config, '2026-10-31')
+  const values = [0, 0.5, 0.999]
+  let i = 0
+  const layout = particleLayout(theme, 12, () => values[i++ % values.length])
+  assert.equal(layout.length, 12)
+  assert.deepEqual(layout.slice(0, theme.emoji.length).map(p => p.emoji), theme.emoji)
+  for (const p of layout) {
+    assert.ok(p.x >= 0 && p.x <= 100)
+    assert.ok(p.duration >= 14 && p.duration <= 28)
+    assert.ok(p.delay <= 0 && -p.delay <= p.duration)
+  }
+  assert.deepEqual(particleLayout(null, 12), [])
+})
diff --git a/tests/security/payloads.mjs b/tests/security/payloads.mjs
index 1c9fdbb1..9a59cb97 100644
--- a/tests/security/payloads.mjs
+++ b/tests/security/payloads.mjs
@@ -120,3 +120,17 @@ export const HOSTILE_README = [
 
 // Long input for catastrophic-backtracking checks
 export const REDOS = 'a'.repeat(50_000) + '!'
+
+// Colours from config.toml [seasons], bound into the background's SVG gradient
+export const HOSTILE_COLORS = [
+  'red',
+  '#fff',
+  '#ffffff;}',
+  '#12345g',
+  'url(javascript:alert(1))',
+  'expression(alert(1))',
+  '#ffffff" onload="alert(1)',
+  'var(--x)',
+  ' #ffffff',
+  ''
+]
diff --git a/tests/security/seasons-config.test.mjs b/tests/security/seasons-config.test.mjs
new file mode 100644
index 00000000..4f349f51
--- /dev/null
+++ b/tests/security/seasons-config.test.mjs
@@ -0,0 +1,60 @@
+// config.toml [seasons] is written into a generated module at build time
+// (scripts/build-seasons.mjs). Its emoji are shown as page text and its colours are bound into
+// the background's SVG gradient. Only known settings with checked values get through.
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { buildSeasonsConfig, seasonsModule, SEASONS_DEFAULTS } from '../../utils/seasons.mjs'
+import { HOSTILE_COLORS, JS_BREAKOUTS, PROTOTYPE_KEYS, XSS_HTML } from './payloads.mjs'
+
+const week = (theme = {}) => ({ from: '01-01', name: 'Snow', emoji: ['❄️'], colors: ['#93c5fd', '#e0f2fe'], ...theme })
+const build = (seasons) => buildSeasonsConfig({ seasons: { enabled: true, ...seasons } })
+
+test('unknown or hostile keys fail the build and never reach the module', () => {
+  for (const key of [...PROTOTYPE_KEYS, ...JS_BREAKOUTS, 'html', 'script']) {
+    const { config, problems } = buildSeasonsConfig({ seasons: { [key]: 1 } })
+    assert.ok(problems.length >= 1, key)
+    assert.deepEqual(Object.keys(config).sort(), Object.keys(SEASONS_DEFAULTS).sort())
+    const nested = build({ week: [week({ [key]: 1 })] })
+    assert.ok(nested.problems.length >= 1, key)
+    assert.ok(!Object.hasOwn(nested.config.weeks[0] ?? {}, key), key)
+  }
+})
+
+test('hostile colours are refused', () => {
+  for (const color of [...HOSTILE_COLORS, ...XSS_HTML, ...JS_BREAKOUTS]) {
+    const { config, problems } = build({ week: [week({ colors: [color, '#ffffff'] })] })
+    assert.ok(problems.length >= 1, color)
+    assert.equal(config.weeks.length, 0, color)
+  }
+})
+
+test('markup, scripts and words are refused as emoji', () => {
+  for (const emoji of [...XSS_HTML, ...JS_BREAKOUTS, 'abc', '"', '&lt;', ' ', '', 42, null]) {
+    const { config, problems } = build({ week: [week({ emoji: [emoji] })] })
+    assert.ok(problems.length >= 1, JSON.stringify(emoji))
+    assert.equal(config.weeks.length, 0)
+  }
+})
+
+test('markup is refused as a name, and dates must be real days', () => {
+  for (const name of [...XSS_HTML, '', 'x'.repeat(41)]) {
+    assert.ok(build({ week: [week({ name })] }).problems.length >= 1, name)
+  }
+  for (const from of ['02-29', '13-01', '1-1', '01-01; x', '__proto__', 20260101]) {
+    assert.ok(build({ week: [week({ from })] }).problems.length >= 1, String(from))
+  }
+  for (const [from, to] of [['2026-10-21', '2026-10-19'], ['2026-02-30', '2026-03-01'], ['x', 'y']]) {
+    const event = { name: 'Event', from, to, emoji: ['⭐'], colors: ['#ffffff', '#000000'] }
+    assert.ok(build({ week: [week()], event: [event] }).problems.length >= 1, `${from} ${to}`)
+  }
+})
+
+test('hostile names stay strings in the generated module: nothing runs', async () => {
+  for (const payload of JS_BREAKOUTS.filter(p => !/[<>]/.test(p))) {
+    const { config, problems } = build({ week: [week({ name: payload })] })
+    assert.deepEqual(problems, [])
+    const mod = await import(`data:text/javascript,${encodeURIComponent(seasonsModule(config))}`)
+    assert.equal(mod.default.weeks[0].name, payload)
+    assert.equal(globalThis.pwned, undefined)
+  }
+})
diff --git a/utils/seasons.mjs b/utils/seasons.mjs
new file mode 100644
index 00000000..7df445f8
--- /dev/null
+++ b/utils/seasons.mjs
@@ -0,0 +1,156 @@
+// Seasonal themes: themed emoji drifting over the background (components/SeasonalParticles.vue)
+// and the topographic lines in the season's colours (components/TopoBackground.vue). Read from
+// config.toml [seasons] by scripts/build-seasons.mjs; anything wrong fails the build, like the
+// other config sections. A theme for every week of the year, plus dated events that take over
+// while they run. Picked in the browser from today's date, so the themes change without a rebuild.
+import { calendarDay } from './coinBubble.mjs'
+
+export const SEASONS_DEFAULTS = {
+  enabled: false,
+  particles: 12,
+  weeks: [],
+  events: []
+}
+
+export const MOTIONS = ['fall', 'rise'] // drift down (leaves, snow) or float up (bubbles, ghosts)
+export const MAX_EMOJI = 8
+export const MAX_NAME = 40
+const MAX_EMOJI_LENGTH = 16 // one emoji, with skin tone / ZWJ sequences / flags
+const MONTH_DAY = /^(\d{2})-(\d{2})$/
+const COLOR = /^#[0-9a-f]{6}$/i
+// One emoji (or a short symbol): no markup, quotes, spaces or escapes
+const EMOJI_UNSAFE = /[<>&"'`\\=\s]/
+const ALPHANUMERIC = /^[a-z0-9]+$/i
+
+// "MM-DD" for a real day of the year (Feb 29 isn't one: not every year has it), or null
+export const monthDay = value => {
+  const match = typeof value === 'string' ? MONTH_DAY.exec(value) : null
+  if (!match) return null
+  const [m, d] = [Number(match[1]), Number(match[2])]
+  const date = new Date(Date.UTC(2025, m - 1, d))
+  return date.getUTCMonth() === m - 1 && date.getUTCDate() === d ? value : null
+}
+
+// The theme's checked settings, or null when any is wrong (the build fails then anyway)
+const checkTheme = (theme, where, problems) => {
+  const out = {}
+  const before = problems.length
+  if (typeof theme !== 'object' || theme === null || Array.isArray(theme)) {
+    problems.push(`${where} must be a table`)
+    return null
+  }
+  const name = typeof theme.name === 'string' ? theme.name.replace(/\s+/g, ' ').trim() : ''
+  if (name && name.length <= MAX_NAME && !/[<>]/.test(name)) out.name = name
+  else problems.push(`${where} name must be 1 to ${MAX_NAME} characters of plain text`)
+
+  const emoji = Array.isArray(theme.emoji) ? theme.emoji : []
+  const goodEmoji = emoji.every(
+    e => typeof e === 'string' && e.length > 0 && e.length <= MAX_EMOJI_LENGTH && !EMOJI_UNSAFE.test(e) && !ALPHANUMERIC.test(e)
+  )
+  if (emoji.length >= 1 && emoji.length <= MAX_EMOJI && goodEmoji) out.emoji = [...emoji]
+  else problems.push(`${where} emoji must be a list of 1 to ${MAX_EMOJI} emoji`)
+
+  const colors = Array.isArray(theme.colors) ? theme.colors : []
+  if (colors.length === 2 && colors.every(c => typeof c === 'string' && COLOR.test(c))) out.colors = colors.map(c => c.toLowerCase())
+  else problems.push(`${where} colors must be two colours like "#f97316"`)
+
+  const motion = theme.motion ?? 'fall'
+  if (MOTIONS.includes(motion)) out.motion = motion
+  else problems.push(`${where} motion must be ${MOTIONS.map(m => `"${m}"`).join(' or ')}`)
+  return problems.length === before ? out : null
+}
+
+const THEME_KEYS = new Set(['name', 'emoji', 'colors', 'motion'])
+const unknownKeys = (table, allowed, where, problems) => {
+  if (typeof table !== 'object' || table === null) return
+  for (const key of Object.keys(table)) if (!allowed.has(key)) problems.push(`${where} ${JSON.stringify(key)} isn't a setting`)
+}
+
+export const buildSeasonsConfig = (toml = {}) => {
+  const section = toml?.seasons ?? {}
+  const config = { ...SEASONS_DEFAULTS, weeks: [], events: [] }
+  const problems = []
+  if (typeof section !== 'object' || Array.isArray(section)) {
+    return { config, problems: ['[seasons] must be a table of settings'] }
+  }
+
+  for (const [key, value] of Object.entries(section)) {
+    if (key === 'enabled') {
+      if (typeof value === 'boolean') config.enabled = value
+      else problems.push('[seasons] enabled must be true or false')
+    } else if (key === 'particles') {
+      if (Number.isInteger(value) && value >= 0 && value <= 40) config.particles = value
+      else problems.push('[seasons] particles must be a whole number from 0 to 40')
+    } else if (key === 'week') {
+      if (!Array.isArray(value)) {
+        problems.push('[seasons] week must be a list of [[seasons.week]] tables')
+        continue
+      }
+      value.forEach((week, i) => {
+        const where = `[[seasons.week]] #${i + 1}`
+        unknownKeys(week, new Set([...THEME_KEYS, 'from']), where, problems)
+        const theme = checkTheme(week, where, problems)
+        const from = monthDay(week?.from)
+        if (!from) problems.push(`${where} from must be a day like "10-29" (month-day, not Feb 29)`)
+        if (theme && from) config.weeks.push({ from, ...theme })
+      })
+    } else if (key === 'event') {
+      if (!Array.isArray(value)) {
+        problems.push('[seasons] event must be a list of [[seasons.event]] tables')
+        continue
+      }
+      value.forEach((event, i) => {
+        const where = `[[seasons.event]] #${i + 1}`
+        unknownKeys(event, new Set([...THEME_KEYS, 'from', 'to']), where, problems)
+        const theme = checkTheme(event, where, problems)
+        const from = calendarDay(event?.from)
+        const to = calendarDay(event?.to)
+        if (!from || !to || from > to) problems.push(`${where} from and to must be dates like 2026-10-19, from first`)
+        else if (theme) config.events.push({ from, to, ...theme })
+      })
+    } else {
+      problems.push(`[seasons] ${JSON.stringify(key)} isn't a setting`)
+    }
+  }
+
+  // The weeks run in order from Jan 1, each until the next one starts, so every day has a theme
+  const starts = config.weeks.map(week => week.from)
+  if (config.weeks.length && starts[0] !== '01-01') problems.push('[[seasons.week]] the first week must start on "01-01"')
+  for (let i = 1; i < starts.length; i++) {
+    if (starts[i] <= starts[i - 1]) problems.push(`[[seasons.week]] #${i + 1} must start after #${i} (${starts[i]} isn't after ${starts[i - 1]})`)
+  }
+  if (config.enabled && !config.weeks.length) problems.push('[seasons] needs [[seasons.week]] themes when enabled')
+  return { config, problems }
+}
+
+// The theme for a day ("YYYY-MM-DD"): an event running that day, or else that day's week. Null
+// when seasons are off. Feb 29 belongs to the week running on Feb 28.
+export const themeFor = (config, day) => {
+  if (!config?.enabled || typeof day !== 'string') return null
+  const event = config.events.find(e => e.from <= day && day <= e.to)
+  if (event) return event
+  const md = day.slice(5)
+  let week = null
+  for (const w of config.weeks) if (w.from <= md) week = w
+  return week
+}
+
+// Where each particle starts and how it moves, picked at random for every page load. `random`
+// returns 0 to 1 (Math.random), so tests can pass their own.
+export const particleLayout = (theme, count, random = Math.random) =>
+  Array.from({ length: theme ? count : 0 }, (_, i) => {
+    const duration = 14 + random() * 14 // seconds to cross the screen
+    return {
+      id: i,
+      emoji: theme.emoji[i % theme.emoji.length],
+      x: Math.round(random() * 1000) / 10, // % across
+      size: Math.round((1 + random() * 1.1) * 100) / 100, // rem
+      duration: Math.round(duration * 10) / 10,
+      delay: -Math.round(random() * duration * 10) / 10, // already on screen at load
+      sway: Math.round((2.5 + random() * 3) * 10) / 10, // seconds per side-to-side
+      spin: Math.round((random() - 0.5) * 720) // degrees over the whole crossing
+    }
+  })
+
+export const seasonsModule = config =>
+  `// Generated by scripts/build-seasons.mjs from config.toml [seasons]. Don't edit.\nexport default ${JSON.stringify(config, null, 2)}\n`

From d21e8eaba86f9ae7f4c179eab34039e941de3167 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Fri, 30 Oct 2026 01:39:17 +0000
Subject: [PATCH 2/2] =?UTF-8?q?Seasons:=20GitHub=20Universe=20(Oct=2028?=
 =?UTF-8?q?=E2=80=9330,=202026)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

GitHub Universe 2026, San Francisco (October 28–29, plus a day of
cooldown): the Octocat, rockets, Copilot and the Golden Gate rising in
GitHub's purple and green. Halloween on Oct 31 is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nginuw5wmUjUSkmQB1J3pS
---
 README.md                  |  2 +-
 config.toml                |  8 ++++++++
 tests/app/seasons.test.mjs | 12 ++++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 1dd5265b..2a51e04d 100644
--- a/README.md
+++ b/README.md
@@ -65,7 +65,7 @@ Faint purple-to-green contour lines (in the season's colours while a seasonal th
 - `draw_seconds` (0–600): time on the page to draw everything. `0` shows it all at once. Reduced-motion settings also show it all at once.
 
 ## Seasonal themes
-Every week of the year has a theme: a few themed emoji drift down (or float up) over the background on every page, and the topographic lines take the theme's two colours. October is spooky (Hacktoberfest, pumpkins, bats, Halloween), December has the winter holidays, and so on. Dated events take over while they run, like All Things Open in Raleigh with laptops, Linux penguins and Raleigh's acorns.
+Every week of the year has a theme: a few themed emoji drift down (or float up) over the background on every page, and the topographic lines take the theme's two colours. October is spooky (Hacktoberfest, pumpkins, bats, Halloween), December has the winter holidays, and so on. Dated events take over while they run, like All Things Open in Raleigh with laptops, Linux penguins and Raleigh's acorns, and GitHub Universe in San Francisco with the Octocat 🐙🐱, rockets, Copilot 🤖 and the Golden Gate 🌉 in GitHub's purple and green.
 - The themes live in `config.toml` under `[seasons]`, checked by `utils/seasons.mjs`; the build fails on a bad value.
   - `enabled`: `true` or `false`.
   - `particles` (0–40): how many emoji at once. Phones show at most 8.
diff --git a/config.toml b/config.toml
index 5cb824e2..c9001dd3 100644
--- a/config.toml
+++ b/config.toml
@@ -400,6 +400,14 @@ emoji = ["💻", "🐧", "🌰", "🎤", "⭐", "🔓"]  # 🌰 Raleigh is the C
 colors = ["#f97316", "#22d3ee"]
 motion = "rise"
 
+[[seasons.event]]
+name = "GitHub Universe"
+from = 2026-10-28
+to = 2026-10-30  # GitHub Universe 2026, San Francisco (October 28–29), plus a day of cooldown
+emoji = ["🐙", "🐱", "🚀", "🌌", "🤖", "🌉", "✨"]  # 🐙🐱 the Octocat, 🤖 Copilot, 🌉 San Francisco
+colors = ["#a371f7", "#3fb950"]  # GitHub's purple and green
+motion = "rise"
+
 [lucky]
 # I'm Feeling Lucky on the 404 page (utils/lucky.mjs): a random blog post opens, or a home page
 # fact or a definition is searched for you, Let Me Google That For You style, in the page.
diff --git a/tests/app/seasons.test.mjs b/tests/app/seasons.test.mjs
index 7b746641..3ca9e724 100644
--- a/tests/app/seasons.test.mjs
+++ b/tests/app/seasons.test.mjs
@@ -33,6 +33,18 @@ test('October is spooky, and All Things Open takes over during the event', () =>
   assert.notEqual(themeFor(config, '2027-10-20').name, 'All Things Open') // dated: one year only
 })
 
+test('GitHub Universe takes over Oct 28–30, 2026, and Halloween is still Halloween', () => {
+  for (const day of ['2026-10-28', '2026-10-29', '2026-10-30']) {
+    const theme = themeFor(config, day)
+    assert.equal(theme.name, 'GitHub Universe', day)
+    assert.ok(theme.emoji.includes('🐙'))
+    assert.deepEqual(theme.colors, ['#a371f7', '#3fb950'])
+  }
+  assert.notEqual(themeFor(config, '2026-10-27').name, 'GitHub Universe')
+  assert.match(themeFor(config, '2026-10-31').name, /Halloween/)
+  assert.notEqual(themeFor(config, '2027-10-29').name, 'GitHub Universe') // dated: one year only
+})
+
 test('a few holidays land in their week', () => {
   assert.match(themeFor(config, '2026-01-01').name, /New Year/)
   assert.match(themeFor(config, '2026-02-14').name, /Valentine/)