diff --git a/.gitignore b/.gitignore
index 02104a3..f4cbd96 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,6 @@ public/
 result
 result-*
 .direnv/
+
+# Zola class-based syntax highlighting — regenerated into static/ on every build
+static/giallo-*.css
diff --git a/CLAUDE.md b/CLAUDE.md
index 43413bf..daeb9c0 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -4,7 +4,13 @@ Project-level guidance for Claude Code working in this repo.
 
 ## Stack
 
-Zola static site generator. Content lives in `content/`, templates in `templates/`, styles in `sass/main.scss`, structured data in `data/`. No npm. Build with `zola build`; serve locally via the launch config in `.claude/launch.json`.
+Zola static site generator. Content lives in `content/`, templates in `templates/`, styles in `sass/main.scss`, structured data in `data/`. No npm.
+
+The toolchain is pinned by the Nix flake (ADR 0007), and config lives in `zola.toml` (a non-default name), so prefer the flake entrypoints over bare `zola`:
+
+- `nix build` — renders the site into `./result` (the rendered `public/` contents).
+- `nix run` (alias `nix run .#serve`) — starts the live-reloading dev server (`zola serve`) at `http://127.0.0.1:1111`.
+- `nix develop` — a shell with the pinned Zola on `PATH` for ad-hoc commands (pass `--config zola.toml`).
 
 ## Design rules
 
diff --git a/README.md b/README.md
index e967654..e25f9b2 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# shanemurphy.space
+# semurphy.com
 
 Personal portfolio and writing site for Shane Murphy. Built with [Zola](https://www.getzola.org/) and deployed to GitHub Pages.
 
@@ -17,19 +17,27 @@ No Node.js, no npm, no JavaScript build tooling.
 
 ## Local development
 
-Install Zola via Homebrew:
+The toolchain is pinned by the Nix flake (see [ADR 0007](docs/adr/0007-nix-build-tooling.md)) — no separate Zola install needed.
+
+Serve locally with live reload:
 
 ```bash
-brew install zola
+nix run
 ```
 
-Serve locally with live reload:
+This runs `zola serve` with the correct config; the site is available at `http://127.0.0.1:1111`.
+
+Build the site into `./result` (the rendered `public/` contents):
 
 ```bash
-zola serve
+nix build
 ```
 
-The site is available at `http://127.0.0.1:1111`.
+Or drop into a shell with the pinned Zola on `PATH` for ad-hoc commands:
+
+```bash
+nix develop
+```
 
 ## Deployment
 
@@ -40,12 +48,12 @@ Pushes to `main` automatically trigger the GitHub Actions workflow at `.github/w
 In the repository's **Settings → Pages**:
 
 - **Source:** GitHub Actions
-- **Custom domain:** `shanemurphy.space`
+- **Custom domain:** `semurphy.com`
 - **Enforce HTTPS:** enabled (once DNS has propagated)
 
 ## Custom domain DNS (Squarespace)
 
-The domain `shanemurphy.space` is registered through Squarespace Domains. The following DNS records must be set in the Squarespace DNS panel:
+The domain `semurphy.com` is registered through Squarespace Domains. The following DNS records must be set in the Squarespace DNS panel:
 
 ### A records (root domain)
 
diff --git a/content/work/fitness.md b/content/work/fitness.md
new file mode 100644
index 0000000..23dfbf3
--- /dev/null
+++ b/content/work/fitness.md
@@ -0,0 +1,5 @@
++++
+title = "Why Sitting is Hard"
+date = 2026-04-06
+draft = true
++++
diff --git a/content/work/virtues.md b/content/work/virtues.md
new file mode 100644
index 0000000..d0f2a6a
--- /dev/null
+++ b/content/work/virtues.md
@@ -0,0 +1,81 @@
++++
+title = "Virtue-Driven Development Considered Harmful"
+date = 2026-06-18
+draft = true
++++
+
+Software teams love virtues. But architectural values are not ideals; they are
+bundles of trade-offs sold under a single flattering name.
+
+- We chose Go because it's simple
+- We reached for microservices because they scale
+- We picked Rust because it's safe
+
+These sound like arguments, but they are slogans until they say what they cost.
+And some don't even survive the asking. "Simplicity" is rarely created or
+destroyed — just moved somewhere you stop looking at it. "Scalability" is a bill
+you may have no reason to pay.
+
+Safety is the interesting one, because it survives. The borrow checker is a
+genuine cost, paid in real units, and it still clears — which is exactly why it
+makes a good ruler for the others.
+
+<!-- TODO: spine of the piece — a virtue has to pass TWO tests:
+       1. Does it name its trade-offs? (honesty)
+       2. Is the thing even worth wanting? (merit)
+     - Simple (Go): fails both. Hides costs; "simplicity" may just be
+       redistributed, not created/destroyed.
+     - Scalable (microservices): fails both. Hides costs; may not be needed.
+     - Safe (Rust): the LOAD-BEARING example. Clears merit outright (safety is
+       genuinely valuable), so only test 1 is left — and the costs (borrow
+       checker, prototyping speed, hiring bar) are real but worth it.
+     Rust isn't the exception to "trade-offs with marketing names" — it's the
+     virtue that earns the name by being honest about the bill. It's what keeps
+     the essay from collapsing into "never trust any virtue" / never build
+     anything. Use it as the pivot into the body, not a closing punchline.
+
+     Names for smuggling a trade-off in as axiomatically good — overlapping
+     lenses on the same dodge, NOT a clean taxonomy (resist the urge to build a
+     tree; the tidiness would itself be a "simple" smuggled in):
+       - Glittering generality — vague virtue-word that wins assent before you
+         can ask "simple for whom?" (warm framing — the one to lead with)
+       - Begging the question / question-begging epithet — the loaded adjective
+         presents the contested claim as a settled premise (cold/logical framing)
+       - Persuasive definition — bake the goodness into the word's meaning so
+         disagreeing sounds anti-virtue (most euphemistic-feeling)
+       - Thought-terminating cliché — "keep it simple" ends analysis vs advances
+       - Presupposing a frame — not really the parent of the others, but a
+         related, less specific sibling: the word ships an unstated context in
+         which it's obviously good; accept the word, accept the frame. Close-
+         feeling to all of them without strictly containing any.
+     Point: a virtue is MOST dangerous when it feels axiomatic — feeling
+     axiomatic is how it dodges the trade-off question. Safety never gets to be a
+     glittering generality (nobody finds the borrow checker warm), so it does the
+     honest work the others skip.
+
+     FORMAT / VOICE: practical, not flowery. Keep the philosophy above as
+     scaffolding in my head, not on the page. The meat is a run of examples, each
+     one shaped:
+       quote you've DEFINITELY heard  ->  the trade-off it hides  ->  who pays it
+     Make each cost land by naming the UNIT it's measured in (network calls, lines
+     of err handling, config branches, onboarding hours). Vague costs read as
+     opinion; a unit reads as proof. "it's slower" is weak; "you traded a 50ns
+     function call for a 5ms RPC that can fail" is the lightbulb.
+     Aim for 5-10 examples: with that many, the reader will feel at least ONE
+     deep in their bones — that's the hit that sells the whole frame.
+
+     Example shortlist (only keep ones the reader has actually heard):
+       - "microservices so teams move independently" -> fn call became a network
+         call: retries, partial failure, tracing, staging never fully up.
+         Independence between teams bought with coupling between services.
+       - "Go is simple" -> no enums/sum types, if err != nil x50. Language stayed
+         simple by making YOUR code carry the complexity.
+       - "no framework, just vanilla, less magic" -> you wrote a worse,
+         undocumented framework inline; onboarding = read all of it.
+       - "configurable so it's flexible" -> every option is a branch to test and a
+         decision pushed onto the user. Flexibility = complexity with a sales team.
+       - "monorepo, everything in one place" -> real honest trade-off to name.
+       - "Postgres for everything, keep it boring" -> real honest trade-off.
+     HONEST COUNTERWEIGHT: keep the Rust/safety section as the one whose bill is
+     real AND worth paying. Earns reader trust; stops the piece reading as
+     "every virtue is a lie." -->
diff --git a/docs/adr/0008-theming-and-dark-mode.md b/docs/adr/0008-theming-and-dark-mode.md
new file mode 100644
index 0000000..5e706e3
--- /dev/null
+++ b/docs/adr/0008-theming-and-dark-mode.md
@@ -0,0 +1,40 @@
+# 0008. Theming and dark mode
+
+- **Status:** Accepted
+- **Date:** 2026-06-20
+
+## Context
+
+The site shipped with a single light palette ("Birch & Cream") defined once in `sass/_palette.scss` and exposed to every component as `--color-*` custom properties. No dark mode existed.
+
+Adding a dark mode raises three questions:
+
+1. **How is a palette represented?** The CSS-custom-property indirection already in place means a theme is nothing more than a re-binding of the six `--color-*` tokens. No component CSS needs to change. This is the single-source-of-truth principle from CLAUDE.md applied to color.
+2. **How does a visitor select a theme, and does an OS preference participate?** Options: manual toggle only; OS preference only (`prefers-color-scheme`); or both, with manual choice overriding the OS default.
+3. **How is a flash of the wrong palette on load avoided?** A purely CSS/`prefers-color-scheme` solution flashes nothing, but a stored manual choice that contradicts the OS will flash unless applied before first paint.
+
+A dark palette was chosen by comparing three candidates in-browser ("Espresso" warm, "Slate" cool-neutral, "Ink" near-black). Slate was selected.
+
+## Decision
+
+**Palette = token re-binding.** Light stays the `:root` default. The dark palette ("Slate") is defined once as a Sass mixin (`slate-tokens`) and applied in two places: under `[data-theme="dark"]` (explicit choice) and under `:root:not([data-theme="light"])` inside a `@media (prefers-color-scheme: dark)` block (OS default). `color-scheme` is set alongside so native form controls and scrollbars match.
+
+**Resolution order:** explicit `[data-theme]` (set by the toggle) → OS `prefers-color-scheme` → light. A stored `"light"` choice opts back out of the OS default via the `:not([data-theme="light"])` guard.
+
+**Persistence and no-flash:** the chosen theme is stored in `localStorage` under `theme`. A tiny inline script in `<head>` applies an explicit stored choice to `<html>` before first paint. With no stored choice, nothing is applied and CSS `prefers-color-scheme` governs — so first-time visitors get their OS preference with zero flash. A second script wires the nav toggle button and keeps its label in sync when the OS preference changes and no explicit choice is set.
+
+Rejected: OS-preference-only (no way to override per-device); manual-only (ignores a preference the visitor already expressed at the OS level); a build-time or server-rendered theme (static host, no per-request state).
+
+## Consequences
+
+**Good:**
+- Adding or swapping a palette is editing six values in one mixin; no component CSS changes.
+- First-time visitors get their OS preference automatically; returning visitors get their explicit choice; neither flashes.
+- The only JavaScript on the site is two small inline scripts — no framework, no build step, consistent with the no-npm constraint.
+
+**Bad / costs:**
+- Two inline scripts in `base.html` are now load-bearing for correct first-paint behavior. They must stay inline (an external file would defeat the no-flash goal).
+- Syntax highlighting is baked in at build time via `zola.toml`'s `catppuccin-latte` (a light theme). In dark mode, highlighted code blocks look out of place. Fixing this requires switching Zola to CSS-class highlighting and shipping per-theme highlight CSS — deferred until a writing post with code actually needs it.
+
+**Foreclosed:**
+- A third user-selectable theme would reintroduce the cycle-style toggle the evaluation phase used; the current toggle is deliberately binary.
diff --git a/docs/adr/0009-apex-domain-migration.md b/docs/adr/0009-apex-domain-migration.md
new file mode 100644
index 0000000..9dcec40
--- /dev/null
+++ b/docs/adr/0009-apex-domain-migration.md
@@ -0,0 +1,34 @@
+# 0009. Apex domain migration to semurphy.com
+
+- **Status:** Accepted
+- **Date:** 2026-06-20
+
+## Context
+
+The site originally launched on `shanemurphy.space` (ADR 0001 hosting, ADR 0002 domain strategy). In practice the `.space` TLD caused friction: several services (form providers, some email validators, link unfurlers, and account-signup allowlists) treat newer/non-`.com` TLDs as suspicious or reject them outright. A shorter, conventional `.com` avoids this class of papercut.
+
+`semurphy.com` was acquired and the apex was migrated (CNAME + `base_url` already point at it; HTTPS live). This ADR records the decision so the architectural changelog stays coherent — `docs/roadmap.md` and `README.md` now say `semurphy.com`, which would otherwise silently contradict ADRs 0001–0002.
+
+## Decision
+
+The canonical apex domain is **`semurphy.com`**, registered through Squarespace Domains, served by GitHub Pages with the same A records and `www` CNAME (`shaneeverittm.github.io`) documented in `README.md`. `static/CNAME` and `zola.toml`'s `base_url` reflect this.
+
+This **amends the naming** used in ADRs 0001 and 0002; it does **not reverse their decisions**:
+
+- ADR 0001 (GitHub Pages hosting) stands unchanged.
+- ADR 0002 (tracker on a subdomain, not a subpath) stands — the subdomain is now `tracker.semurphy.com`.
+
+The old `shanemurphy.space` continues to resolve and redirects to the canonical apex, so existing links don't break.
+
+## Consequences
+
+**Good:**
+- Conventional `.com` removes TLD-based rejection from third-party services.
+- No structural change: same host, same DNS shape, same deploy pipeline.
+
+**Bad / costs:**
+- Two registrations to keep renewed for as long as the `.space` redirect is maintained.
+- Any hard-coded `shanemurphy.space` strings (e.g. the contact email `mail@shanemurphy.space` in `zola.toml`) must be migrated deliberately — email in particular depends on where the mailbox actually lives and is intentionally left for a separate decision.
+
+**Foreclosed:**
+- Nothing. The redirect preserves the old domain's inbound links indefinitely if desired.
diff --git a/docs/adr/README.md b/docs/adr/README.md
index ffa519f..332d57b 100644
--- a/docs/adr/README.md
+++ b/docs/adr/README.md
@@ -27,3 +27,5 @@ A starter template is at `0000-template.md`. Copy it, renumber, fill it in.
 | [0005](0005-progression-rule-encoding.md) | Encoding progression rules in the program TOML | Accepted |
 | [0006](0006-session-json-schema.md) | Session JSON schema | Accepted |
 | [0007](0007-nix-build-tooling.md) | Nix flake as the build toolchain | Accepted |
+| [0008](0008-theming-and-dark-mode.md) | Theming and dark mode | Accepted |
+| [0009](0009-apex-domain-migration.md) | Apex domain migration to semurphy.com | Accepted |
diff --git a/docs/roadmap.md b/docs/roadmap.md
index b7b9814..eb45041 100644
--- a/docs/roadmap.md
+++ b/docs/roadmap.md
@@ -5,7 +5,7 @@ Living document. Updated as phases complete or assumptions change. The original
 
 ## Context
 
-The site is a Zola SSG at shanemurphy.space (GitHub Pages, GitHub Actions deploy). It includes a workout program in
+The site is a Zola SSG at semurphy.com (GitHub Pages, GitHub Actions deploy). It includes a workout program in
 `data/workout_program.toml` with auto-derived volume targets per muscle group.
 
 The goal is a workout tracker that:
@@ -47,7 +47,7 @@ These touch every later phase, so resolving them first is load-bearing. Each wil
 
 1. **Hosting target.** Currently on GitHub Pages. The tracker write path needs a serverless function that can commit to
    the repo via the GitHub API.
-2. **Domain strategy.** Subdomain (`tracker.shanemurphy.space`) vs subpath (`/tracker`).
+2. **Domain strategy.** Subdomain (`tracker.semurphy.com`) vs subpath (`/tracker`).
 3. **Auth between phone and Worker.** Single-user shared secret vs OAuth-with-GitHub vs nothing-but-obscurity.
 4. **CI rebuild filtering.** Whether session-only commits should skip the tracker SPA rebuild.
 5. **Structured progression rules in TOML.** Whether to encode `progression = { kind, increment, cadence, deload }` now
@@ -102,9 +102,9 @@ without bundling them into a SPA build.
   adds one).
 - Verify program.json is fetchable from a deployed page.
 
-**Deliverable:** A live URL like `shanemurphy.space/program.json` that returns the compiled program.
+**Deliverable:** A live URL like `semurphy.com/program.json` that returns the compiled program.
 
-**Ready when:** `curl https://shanemurphy.space/program.json` returns valid JSON matching the schema agreed in Phase 0.
+**Ready when:** `curl https://semurphy.com/program.json` returns valid JSON matching the schema agreed in Phase 0.
 
 ---
 
diff --git a/flake.nix b/flake.nix
index 47dca0e..b7be6c9 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,13 +1,19 @@
 {
-  description = "shanemurphy.space — Zola static site";
+  description = "semurphy.com — Zola static site";
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
   };
 
-  outputs = { self, nixpkgs }:
+  outputs =
+    { self, nixpkgs }:
     let
-      systems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      systems = [
+        "x86_64-linux"
+        "aarch64-linux"
+        "x86_64-darwin"
+        "aarch64-darwin"
+      ];
       forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f nixpkgs.legacyPackages.${system});
     in
     {
@@ -31,29 +37,12 @@
       devShells = forAllSystems (pkgs: {
         default = pkgs.mkShell {
           packages = [ pkgs.zola ];
-          # `nix develop` drops into a bash subshell. When launched from Warp,
-          # emit Warp's bootstrap escape sequence so the subshell gets blocks,
-          # completions, etc.
-          #
-          # Two guards:
-          #   - $- contains `i` only for an interactive shell. Under direnv the
-          #     hook runs non-interactively inside the already-warpified host
-          #     shell, so there's no subshell to bootstrap — skip it there.
-          #   - $TERM_PROGRAM makes it a no-op outside Warp.
-          shellHook = ''
-            case $- in
-              *i*)
-                if [ "$TERM_PROGRAM" = "WarpTerminal" ]; then
-                  printf '\eP$f{"hook": "SourcedRcFileForWarp", "value": { "shell": "bash" }}\x9c'
-                fi
-                ;;
-            esac
-          '';
         };
       });
 
       # `nix run` / `nix run .#serve` → live-reloading dev server.
-      apps = forAllSystems (pkgs:
+      apps = forAllSystems (
+        pkgs:
         let
           serve = pkgs.writeShellScriptBin "serve" ''
             exec ${pkgs.zola}/bin/zola --config zola.toml serve "$@"
@@ -65,6 +54,7 @@
             type = "app";
             program = "${serve}/bin/serve";
           };
-        });
+        }
+      );
     };
 }
diff --git a/sass/_palette.scss b/sass/_palette.scss
index d7c09ac..1a4d5a2 100644
--- a/sass/_palette.scss
+++ b/sass/_palette.scss
@@ -1,4 +1,4 @@
-// ─── Birch & Cream — raw stops ───────────────────────────────────────────────
+// ─── Birch & Cream — raw stops (light) ───────────────────────────────────────
 
 $parchment : #F7F2E8;   // lightest bg
 $raw-linen : #E6DBCB;   // surface / footer bg
@@ -7,7 +7,31 @@ $caramel   : #9A7A5E;   // accent text, labels, links
 $bark      : #634D3A;   // body / supporting text
 $espresso  : #3A2B1E;   // headings, strong text
 
-// ─── Semantic CSS custom properties ──────────────────────────────────────────
+// ─── Slate — raw stops (dark) ────────────────────────────────────────────────
+
+$slate-bg      : #14171A;   // lightest bg
+$slate-surface : #1C2024;   // surface / footer bg
+$slate-border  : #2C3238;   // borders, dividers
+$slate-muted   : #8A95A0;   // accent text, labels, links
+$slate-body    : #C2CAD2;   // body / supporting text
+$slate-heading : #F0F3F6;   // headings, strong text
+
+// ─── Semantic tokens ─────────────────────────────────────────────────────────
+//
+// Every component reads from --color-*. A theme is just a re-binding of these
+// six variables. Resolution order:
+//   1. Explicit choice via [data-theme] (set by the toggle in base.html).
+//   2. OS preference via prefers-color-scheme, when no explicit choice is made.
+//   3. Light (the :root default) otherwise.
+
+@mixin slate-tokens {
+  --color-bg       : #{$slate-bg};
+  --color-surface  : #{$slate-surface};
+  --color-border   : #{$slate-border};
+  --color-muted    : #{$slate-muted};
+  --color-body     : #{$slate-body};
+  --color-heading  : #{$slate-heading};
+}
 
 :root {
   --color-bg       : #{$parchment};
@@ -16,4 +40,21 @@ $espresso  : #3A2B1E;   // headings, strong text
   --color-muted    : #{$caramel};
   --color-body     : #{$bark};
   --color-heading  : #{$espresso};
+
+  color-scheme: light;
+}
+
+// Explicit dark choice wins everywhere.
+[data-theme="dark"] {
+  @include slate-tokens;
+  color-scheme: dark;
+}
+
+// System preference — applied only when the visitor hasn't explicitly chosen.
+// An explicit [data-theme="light"] opts back out.
+@media (prefers-color-scheme: dark) {
+  :root:not([data-theme="light"]) {
+    @include slate-tokens;
+    color-scheme: dark;
+  }
 }
diff --git a/sass/main.scss b/sass/main.scss
index 1e77afb..33433ca 100644
--- a/sass/main.scss
+++ b/sass/main.scss
@@ -15,6 +15,7 @@ body {
   min-height    : 100dvh;
   display       : flex;
   flex-direction: column;
+  transition    : background-color 0.2s ease, color 0.2s ease;
 }
 
 main {
@@ -69,8 +70,9 @@ a {
 }
 
 .nav-links {
-  display: flex;
-  gap    : 1.5rem;
+  display    : flex;
+  align-items: center;
+  gap        : 1.5rem;
 
   a {
     font-family   : sans-serif;
@@ -80,6 +82,26 @@ a {
   }
 }
 
+.theme-toggle {
+  font-family   : sans-serif;
+  font-size     : 11px;
+  letter-spacing: 0.06em;
+  text-transform: uppercase;
+  color         : var(--color-muted);
+  background    : transparent;
+  border        : 1px solid var(--color-border);
+  border-radius : 20px;
+  padding       : 4px 11px;
+  cursor        : pointer;
+  min-width     : 5.5em;
+  transition    : color 0.15s ease, border-color 0.15s ease;
+
+  &:hover {
+    color       : var(--color-heading);
+    border-color: var(--color-muted);
+  }
+}
+
 // ─── Hero ─────────────────────────────────────────────────────────────────────
 
 .hero {
diff --git a/templates/base.html b/templates/base.html
index 29a0aba..72057d5 100644
--- a/templates/base.html
+++ b/templates/base.html
@@ -6,6 +6,23 @@
   <title>{% block title %}{{ config.title }}{% endblock title %}</title>
   <meta name="description" content="{% block description %}{{ config.description }}{% endblock description %}">
   <link rel="stylesheet" href="{{ get_url(path='main.css') }}">
+  {# Syntax-highlight palettes (Zola class-based). The media attributes are the
+     no-JS fallback: the OS preference picks one. The theme script overrides them
+     to honor an explicit toggle choice. #}
+  <link id="hl-light" rel="stylesheet" href="{{ get_url(path='giallo-light.css') }}" media="(prefers-color-scheme: light)">
+  <link id="hl-dark"  rel="stylesheet" href="{{ get_url(path='giallo-dark.css') }}"  media="(prefers-color-scheme: dark)">
+  {# Apply an explicit choice before first paint to avoid a flash of the wrong
+     palette. With no stored choice, CSS prefers-color-scheme handles it. #}
+  <script>
+    (function () {
+      var t = localStorage.getItem("theme");
+      if (t !== "dark" && t !== "light") return;          // no explicit choice ⇒ let CSS decide
+      document.documentElement.setAttribute("data-theme", t);
+      var l = document.getElementById("hl-light"), d = document.getElementById("hl-dark");
+      if (l) l.media = t === "light" ? "all" : "not all";
+      if (d) d.media = t === "dark"  ? "all" : "not all";
+    })();
+  </script>
   {% block extra_head %}{% endblock extra_head %}
 </head>
 <body>
@@ -17,6 +34,7 @@
         <a href="{{ get_url(path='/work') }}">Work</a>
         <a href="{{ get_url(path='/writing') }}">Writing</a>
         <a href="{{ get_url(path='/fitness') }}">Fitness</a>
+        <button type="button" id="theme-toggle" class="theme-toggle" aria-label="Switch theme">Light</button>
       </div>
     </div>
   </nav>
@@ -42,5 +60,43 @@
     </div>
   </footer>
 
+  {# Light/Dark toggle. No stored choice ⇒ follow the OS via prefers-color-scheme. #}
+  <script>
+    (function () {
+      var root = document.documentElement;
+      var btn = document.getElementById("theme-toggle");
+      var mq = window.matchMedia("(prefers-color-scheme: dark)");
+
+      var hlLight = document.getElementById("hl-light");
+      var hlDark = document.getElementById("hl-dark");
+
+      function effective() {
+        var t = localStorage.getItem("theme");
+        if (t === "dark" || t === "light") return t;
+        return mq.matches ? "dark" : "light";
+      }
+      function render() {
+        var dark = effective() === "dark";
+        if (btn) btn.textContent = dark ? "Dark" : "Light";
+        if (hlLight) hlLight.media = dark ? "not all" : "all";
+        if (hlDark) hlDark.media = dark ? "all" : "not all";
+      }
+
+      render();
+      if (btn) {
+        btn.addEventListener("click", function () {
+          var next = effective() === "dark" ? "light" : "dark";
+          root.setAttribute("data-theme", next);
+          localStorage.setItem("theme", next);
+          render();
+        });
+      }
+      // Track OS changes while the visitor has made no explicit choice.
+      mq.addEventListener("change", function () {
+        if (localStorage.getItem("theme") === null) render();
+      });
+    })();
+  </script>
+
 </body>
 </html>
diff --git a/zola.toml b/zola.toml
index 0c69e06..55006c0 100644
--- a/zola.toml
+++ b/zola.toml
@@ -5,7 +5,9 @@ compile_sass = true
 minify_html = false
 
 [markdown.highlighting]
-theme = "catppuccin-latte"
+style = "class"
+light_theme = "catppuccin-latte"
+dark_theme = "catppuccin-mocha"
 
 [extra]
 hero_headline = "Engineer,<br>musician,<br>human."
@@ -14,7 +16,7 @@ hero_tags = ["Software", "Space", "Music", "Gaming"]
 
 github = "https://github.com/ShaneEverittM"
 linkedin = "https://www.linkedin.com/in/shane-everitt-murphy/"
-email = "mail@shanemurphy.space"
+email = "mail@semurphy.com"
 
 [[extra.about_facts]]
 key = "Location"