Accessibility Not Optional

Accessibility doesn’t reduce to the other design principles. Gestalt, Fitts, Hick, and Shannon describe how perception works for a typical visual user. Accessibility asks: what about everyone else? It spans perceptual physics (contrast, color blindness), motor constraints (keyboard nav, touch targets), law (WCAG, ADA), and ethics. No single framework covers it.

The best practical guide is Material Design’s accessibility foundations. It’s comprehensive, maintained, and CC-BY 4.0. Google writes it as a committee, but the committee did good work here.

Key ingredients for an agent:

• Contrast ratios: 4.5:1 for text, 3:1 for large text and UI components
• Touch targets: 48×48dp minimum
• Focus indicators for keyboard navigation
• Semantic HTML and ARIA roles
• prefers-reduced-motion support
• Color not as the sole indicator of state
• Text alternatives for images

The WCAG guidelines are the legal standard. Material Design translates them into actionable design patterns. Use both: WCAG for compliance, Material for implementation.

Reference implementations

• NetNewsWire (MIT) — native Apple a11y: VoiceOver, keyboard navigation, dark mode, reader typography.
• Posting (Apache-2.0) — terminal a11y: focus management, keyboard-first interaction, command palette, theme system with density modes.

This is the one area where “good enough” is not good enough. Every other design principle degrades gracefully — a slightly wrong line height is still readable, a slightly slow transition is still navigable. An inaccessible interface is a locked door.