Appendix — Accessibility

Stack appendix for the Sigma Engineering Standards. Covers accessibility and inclusive design — what we hold ourselves to so that what we build works for everyone. Inclusiveness, kindness, and consideration are part of how we work, not a compliance checkbox; this appendix makes the default explicit. It is also the bar for any AI agent building interfaces in our repos: match it, and surface any deviation (see §8 of the standard, AI Agent Rules of Engagement).

1. Accessible by Default

Accessibility is the baseline, not a feature. It's designed and built in from the first commit — never a retrofit, never a backlog item labelled "a11y later". Retrofitting is more work for a worse result.
Assume a wider audience than yourself. People use keyboards, screen readers, switch devices, magnification, captions, and reduced motion. People are also tired, on a small screen, in bright sun, one-handed. Building for them is building for everyone.
Kindness is a requirement. Clear language, forgiving forms, honest error messages, no dark patterns. Consideration for the person on the other side of the screen is a quality bar, and we hold it.

2. The Bar — WCAG 2.2 AA

WCAG 2.2 Level AA is the minimum for anything user-facing. Its four principles — Perceivable, Operable, Understandable, Robust — are the frame.
Verified, not assumed. Accessibility is reviewed like any other requirement (see the Frontend Accessibility Review playbook) and tested with real assistive technology — not just an automated scan, which catches perhaps a third of issues.

3. What "Default" Means in Practice

Semantic HTML first. A real <button>, <a>, <label>, <nav>, correct heading order — the platform gives you accessibility for free when you use the right element. ARIA patches what the platform can't express; it's not a substitute.
Keyboard-complete. Everything operable by mouse is operable by keyboard, in a logical order, with a visible focus indicator and no keyboard traps.
Screen-reader coherent. Meaningful names, roles, and states; images have alt text (or are marked decorative); live regions announce change.
Perceivable. Text contrast ≥ 4.5:1 (3:1 for large text and UI), never colour alone to carry meaning, content reflows to 320px without loss.
Forgiving forms. Labels tied to inputs, errors described in text and linked to the field, no time pressure you don't truly need.
Respect preferences. Honour prefers-reduced-motion and prefers-color-scheme; don't autoplay or flash.
Internationalisation. lang set, text allowed to expand, layouts mirror for RTL, dates/numbers/names localised.

4. Beyond the Interface

Consideration doesn't stop at the UI. Documentation is written to be understood (see the Documentation Review playbook); diagrams carry text alternatives; communication is plain and patient. The same DNA, everywhere.

5. The Checklist (PR-time)

[ ] Semantic HTML; ARIA only where the platform can't express it
[ ] Fully keyboard operable, logical focus order, visible focus
[ ] Names/roles/states correct; images have alt text or are marked decorative
[ ] Contrast meets AA; meaning never carried by colour alone
[ ] Forms have linked labels and text error messages
[ ] prefers-reduced-motion / prefers-color-scheme respected
[ ] Checked with a screen reader, not just an automated scan

References

Sigma Accessibility Appendix — v1.0 · pairs with main standard v1.3