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
Design Rules	Paired right/wrong calls across icons, type, color, IA, interaction, copy

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:

• No layout shift on dynamic content
• Animations have reduced motion support
• Touch targets are 44px minimum
• 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
• 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