Practical access features.
The interface uses headings and landmarks, a skip link, labelled native controls, visible keyboard focus and responsive layouts. Menus and FAQs use native details/summary elements. A valid result receives focus; custom validation errors use an alert.
No animation, drag-and-drop, chart interpretation, microphone or mouse-only input is needed. Working is selectable text and can be downloaded or printed.
The requested palette.
Headings and text use #091540, secondary #1B2CC1, accent #7692FF and light background #ABD2FA. Dark text stays on light or accent surfaces; secondary blue is used for borders and selected details. Meaning is conveyed by words, not colour alone.
Forced-colour accessibility modes and native browser controls may use system colours. The interface does not disable browser zoom.
Keyboard and narrow screens.
Use Tab and Shift+Tab to move, Enter or Space for menus/FAQs, and Escape to close an open header menu. All Tools contains the six direct links and the index. Navigation wraps where needed, and dropdowns are constrained to narrow screens.
Long exact numbers wrap rather than forcing the entire page sideways. A wrapped line does not change the digits. Text downloads can help when a number is difficult to inspect visually.
Validation, syntax and no-JavaScript behaviour.
Input hints explain the decimal/e syntax and bounds. Native required/range checks are combined with plain-language parsing/domain errors. After correcting an input, calculate again; previous working is removed on edits to avoid a misleading stale answer.
Tools require a modern browser with JavaScript and BigInt support. Without JavaScript, controls remain disabled so they do not submit to a server. On WordPress, methods, FAQs and information text are still rendered and readable. The standalone preview requires JavaScript for navigation too.
Testing and known boundaries.
Responsive, keyboard-menu, result-focus, validation, download and print behaviour are checked in a modern Chromium environment. This is not a claim of formal WCAG certification or exhaustive testing with every assistive technology, browser, zoom level or printer.
The active WordPress theme and other installed software can add behaviour independently. Screen readers may pronounce caret notation such as 10^-4 differently; the nearby step text explains the exponent in words.
Report a barrier.
Use Contact to describe the tool, action, browser/device and barrier. Share only what is necessary; no private numbers or student details are needed. Mention a preferred format or adjustment if helpful. The operator should review the report and possible alternatives without promising a fixed response time.