name: emil-design-engineering description: Design engineering principles and patterns for building polished, accessible web interfaces. Use this skill when building UI components, reviewing frontend code, implementing forms, handling touch interactions, optimizing performance, or creating marketing pages. Triggers on: design engineering, UI polish, input fields, form validation, button states, touch devices, mobile UX, accessibility, a11y, keyboard navigation, aria labels, font rendering, typography, layout shift, z-index, animations, transitions, easing, hover effects, tap targets, iOS Safari, prefers-reduced-motion, marketing pages, landing pages, dark mode, theme switching, scrollbars, gradients, shadows, virtualization, preloading.

Emil's Design Engineering Principles

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

Quick Reference

Category	When to Use
Animations	Enter/exit transitions, easing, springs, performance
UI Polish	Typography, visual design, layout, colors
Forms & Controls	Inputs, buttons, form submission
Touch & Accessibility	Mobile, touch devices, keyboard nav, a11y
Component Design	Compound components, composition, props API
Marketing	Landing pages, blogs, docs sites
Performance	Virtualization, preloading, optimization

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. Ensure 44px minimum tap targets. 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

Mistake	Fix
`transition: all`	Specify exact properties
Hover effects on touch	Use `@media (hover: hover)`
Font weight change on hover	Use consistent weights
Animating `height`/`width`	Use `transform` and `opacity` only
No reduced motion support	Add `prefers-reduced-motion` query
z-index: 9999	Use fixed scale or `isolation: isolate`
Custom page scrollbars	Only customize scrollbars in small elements

Review Checklist

When reviewing UI code, check:

Reference Files

For detailed guidance on specific topics:

animations.md - Easing, timing, springs, performance
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

emil-design-engineering

SKILL.md