Accessibility

The Interactive Primer is meant for everyone — "from the age of 5 to 105." We want the whole tree of knowledge to be usable with a keyboard, a screen reader, magnification, and reduced-motion or high-contrast settings, not just a mouse and a steady gaze. We aim to meet the Web Content Accessibility Guidelines (WCAG) 2.1, Level AA. This is an open-source project that improves continuously, and accessibility is part of how we build every new lesson.

• Every control is a real, focusable button, link, or form field with a descriptive label.
• The site is operable by keyboard, with a visible focus outline and a "Skip to main content" link on every page.
• We honour your operating system's reduce motion setting, dropping non-essential animation and transitions.
• Light, dark, and high-contrast "fun" themes (chosen from the menu) all use colour combinations that aim to meet AA contrast, and colour is never the only way information is conveyed.
• Interactive state — such as your confidence rating — is announced to screen readers, and status messages use polite live regions.
• Mathematics is rendered with an accessible MathML representation for assistive technology, and diagrams provide captions or spoken narration where available.
• Text is set in scalable units, so browser zoom and larger default font sizes work.

We'd rather be honest about what isn't there yet. We're actively working on these:

• The tree / graph explorer is not yet fully keyboard- or screen-reader-operable. The draggable map on the "Explore the tree" page and the small map at the top and bottom of each lesson are currently pointer-driven.
  Workaround: use the concept search box (top-left of the explorer and every lesson) to jump straight to any concept by name, and the prerequisite / next links shown in each lesson to move through the tree.
• Some diagrams and animations do not yet have a full text description of what they show.
• Mathematics accessibility depends on your browser and assistive technology's support for MathML, which varies.
• The site has not yet had an independent accessibility audit, and we do not yet run automated accessibility checks.

• Open the menu (top-right) to switch the theme (light / dark / fun) and the language.
• Use your browser's zoom (usually Ctrl/Cmd and +) to enlarge everything.
• Turn on reduce motion in your operating system's settings and the site will respect it automatically.

The Interactive Primer is partially conformant with WCAG 2.1 Level AA: most of the site meets the standard, but the graph explorer described above does not yet fully conform. We are treating that as our top accessibility priority.

If you hit a barrier, or something here doesn't work for you, please tell us — it directly shapes what we fix next. Open a thread in GitHub Discussions or file an issue on GitHub. Let us know the page, what you were trying to do, and the browser and assistive technology you were using, and we'll do our best to help and to fix the underlying problem.

Last reviewed: 1 July 2026.