Principia — marketing site

The advertising site for Principia, a browser-based MBSE and assurance platform. Published at https://principia-modelling.com/.

The platform itself lives in a separate repository; this one contains only the site. The pre-2026 prototype that used to live here is preserved at the prototype-archive tag.

Layout

index.html          landing page
case-study.html     atmosphere detritiation system walkthrough
assets/css/         tokens.css (design tokens) + site.css (components)
assets/js/site.js   nav, lightbox, matrix hint
assets/img/shots/   committed WebP screenshots, two widths each
tools/              image pipeline, OG card generator, verification suite
docs/superpowers/   design spec and implementation plan

No build step

There is deliberately no toolchain — no Node, no bundler, no CI pipeline. Edit the HTML and CSS directly and commit. Generated assets are committed because nothing runs in CI.

Two rules keep it that way:

• assets/css/tokens.css is the only file allowed to contain hex colours. Everything else uses var(--token).
• No external requests. No webfonts, CDNs, analytics or third-party scripts.

Verify before committing

python3 tools/check-site.py

This is the test suite. It checks tag balance, page metadata, relative paths, that every referenced file exists, colour contrast against WCAG AA, declared image dimensions against the actual files, the image size budget, matrix accessibility, the JS budget, and the copy rules. It must print PASS.

Regenerating screenshots

./tools/build-images.sh /path/to/deck.pptx
python3 tools/make-og-card.py

Requires cwebp (brew install webp) and Pillow. The source deck is private and git-ignored — never commit it.

Editing the nav or footer

Both pages carry byte-identical blocks between the <!-- nav:start --> / <!-- nav:end --> and <!-- footer:start --> / <!-- footer:end --> markers. Change one, copy it to the other; check-site.py fails if they diverge. This is the accepted cost of having no templating. At four or five pages, revisit it.

Deployment

GitHub Pages, Settings → Pages → Deploy from a branch → main / (root). Pushing to main publishes. .nojekyll stops Jekyll touching the files.

The site is served at https://principia-modelling.com/ via the CNAME file at the repo root. wrwei.github.io/Principia/ 301-redirects to it.

Changing the domain

Asset paths are relative throughout and need no attention, but 12 absolute URLs do, and tools/check-site.py asserts two of them. All of these must move together:

File	Occurrences
CNAME	the hostname itself
index.html	4 — canonical, og:url, og:image, JSON-LD url
case-study.html	3 — canonical, og:url, og:image
sitemap.xml	2
robots.txt	1 — the Sitemap: line
tools/check-site.py	1 — CANONICAL_BASE
README.md	1 — the link above

DNS for the current domain: four apex A records to 185.199.108.153, 185.199.109.153, 185.199.110.153, 185.199.111.153, and a www CNAME to wrwei.github.io. — GitHub then redirects www to the apex.