Emil Design Engineering

Emil's Design Engineering Principles

A comprehensive guide for building polished, accessible web interfaces based on Emil Kowalski's design engineering practices.

Choose the scope

• Broad design-engineering pass: read the references that match the surface being built or reviewed. Check structure, interaction, accessibility, visual craft, and performance together.
• Focused polish pass: when a component or small region "feels off," read focused-polish.md. Keep the pass local unless the cause is a shared token, primitive, or layout rule.

For motion work, follow ../animate/references/canonical-policy.md as the canonical policy. It wins when this skill or a companion reference makes a stronger or conflicting claim. Route to animate, css-animations, animation-performance, or animation-accessibility as appropriate.

Quick Reference

Core Principles

1. No Layout Shift

Dynamic elements should cause no layout shift. Use hardcoded dimensions, font-variant-numeric: tabular-nums for changing numbers, and avoid font weight changes on hover/selected states.

2. Touch-First, Hover-Enhanced

Design for touch first, then add hover enhancements. Disable hover effects on touch devices. Meet the WCAG target-size baseline and aim for a comfortable 44px touch target. Never rely on hover for core functionality.

3. Keyboard Navigation

Tabbing should work consistently. Only allow tabbing through visible elements. Ensure keyboard navigation scrolls elements into view with scrollIntoView().

4. Accessibility by Default

Every animation needs prefers-reduced-motion support. Every icon button needs an aria label. Every interactive element needs proper focus states.

5. Speed Over Delight

Product UI should be fast and purposeful. Skip animations for frequently-used interactions. Marketing pages can be more elaborate.

Decision Flowcharts

Should I Animate This?

Will users see this 100+ times daily?
├── Yes → Don't animate
└── No
    ├── Is this user-initiated?
    │   └── Yes → Animate with ease-out (150-250ms)
    └── Is this a page transition?
        └── Yes → Animate (300-400ms max)

What Easing Should I Use?

Is the element entering or exiting?
├── Yes → ease-out
└── No
    ├── Is it moving on screen?
    │   └── Yes → ease-in-out
    └── Is it a hover/color change?
        ├── Yes → ease
        └── Default → ease-out

Common Mistakes

Review Checklist

When reviewing UI code, check:

• No layout shift on dynamic content
• Animations have reduced motion support
• Pointer targets meet WCAG 2.2 AA; touch-heavy controls aim for 44px
• Hover effects disabled on touch devices
• Keyboard navigation works properly
• Icon buttons have aria labels
• Forms submit with Enter/Cmd+Enter
• Inputs are 16px+ to prevent iOS zoom
• No transition: all
• z-index uses fixed scale

Reference Files

For detailed guidance on specific topics:

• animations.md - Easing, timing, springs, performance
• focused-polish.md - Local visual diagnosis and high-value detail work
• ui-polish.md - Typography, shadows, gradients, scrollbars
• forms-controls.md - Inputs, buttons, form patterns
• touch-accessibility.md - Touch devices, keyboard nav, a11y
• component-design.md - Compound components, composition, props API
• marketing.md - Landing pages, blogs, docs
• performance.md - Virtualization, preloading, optimization