Design Engineering

Design Engineering Skill

Based on Emil Kowalski's design engineering philosophy — UI polish, component craftsmanship, and the compound value of invisible details.

Core Principles

• Taste is trainable. Develops through studying exceptional work, reverse-engineering animations, and intentional practice.
• Invisible details create love. Most UI refinements users never consciously register — but combined they produce something stunning.
• Beauty differentiates. When functionality is table stakes, aesthetic excellence becomes genuine leverage.

Anti-Slop Visual & Structural Checklist

Defaults that signal machine-generated UI ("AI slop"). Each is a falsifiable rule to uphold:

• Avoid full-bleed saturated gradient backgrounds (purple-to-pink/blue hero washes) and gradient headlines (background-clip: text). Use solid ink or warm neutral tinting.
• Avoid emoji as load-bearing decoration (emoji as icons, bullet markers, or section badges). Use a real icon set (Lucide/Phosphor/Heroicons) or typographic hierarchy.
• Avoid the 3-equal-column card grid with icon-above-heading tiles, nested cards-in-cards, or cards with thick coloured left-edge side stripes.
• Avoid hand-drawn fake imagery in SVG (synthetic "photos", invented logos, faux screenshots). Use a real asset or an honest labeled placeholder.
• Avoid fake re-drawn UI chrome (mock browser bars with traffic-light dots, mock IDE title bars, faux phone frames). Let content stand cleanly or use real screenshots in a <figure>.
• Avoid default-attractor sameness (Hero → 3 features → CTA → footer). Pick intentional macrostructures and vary heading placement, column rhythm, and divider language.
• Avoid the overused default font stack (Inter/Roboto on system-ui with no pairing). Apply the 2+1 rule (display + body + at most 1 outlier face in <=2 slots).
• Avoid italic headers: headings and display type are always roman (font-style: normal). Never use single-word italic emphasis inside a headline.

Pre-Emit Self-Critique (Six Axes)

Before marking any UI output complete, score it 1–5 on these six axes (score <3 on any axis triggers a revision pass):

The 8 Interactive States Discipline

Every interactive element (button, input, select, card, tab, switch) must explicitly handle all 8 states in code. Styling only default + hover is an immediate defect:

Input Fields & Zero Layout Shift

Input fields, textareas, and selects are where almost-right UIs break:

• Constant border width (1px everywhere): Never change border-width between default, hover, focus, error, or disabled states. State changes go to background-color, outline, box-shadow, or border-color.
• Reserved transparent outline: Initialize with outline: 2px solid transparent; outline-offset: 1px; so activating :focus-visible never shifts layout or thrashes paint.
• Matched component heights: Input height MUST equal adjacent button height (base floor 44px for touch targets).
• Reserved helper-text slot: Allocate min-height: 1lh for helper/error text so appearing validation messages do not push downstream page content.

Responsive Non-Negotiables

Verify every layout at 320px, 375px, 414px, and 768px:

• No horizontal scroll: Apply overflow-x: clip (never hidden) on both html and body.
• Single-line clickable affordances: Buttons, primary nav links, footer links, and CTAs must never wrap to two lines. Shorten label or reflow parent container.
• Image grid tracks: Always use minmax(0, 1fr) instead of bare 1fr to prevent image intrinsic dimensions from blowing out the grid.
• Header wrapping: Display headers must include overflow-wrap: anywhere; min-width: 0;.

Locked Tokens Discipline

• All colors and typography must bind to declared tokens (var(--color-accent), var(--font-display)).
• Never improvise inline hex / rgb / OKLCH values in components mid-build.
• Keep accent footprint under ~5% of viewport area (accent is for focal emphasis, not surface fill).
• Tint neutral surfaces toward the primary anchor hue (minimum 0.005 chroma in OKLCH) — avoid flat #000 / #fff.

Minimum-Scale Floors

Accessibility-grounded hard thresholds. Going below these is a defect, not a style choice:

Treat these as the lower bound, not the target. Captions and footnotes may approach the floor; primary content should sit comfortably above it.

Context-First & Pre-Flight Discipline

High-fidelity work MUST be rooted in real context before any pixels are produced:

• Run Pre-Flight Scan: Inspect existing design.md, package font stacks, palette tokens (:root, Tailwind @theme), motion libraries (framer-motion, motion, gsap), and spacing scale.
• Preserve existing design systems: Never overwrite established tokens or typography unless explicitly asked.
• Lift exact values: Copy real token variable names and spacing classes straight from source. Do NOT reconstruct token values from memory.

Question-Budget Gate

Calibrate questions to how bounded the ask is, then proceed:

• Rich context + bounded ask → ask nothing, build. Example: "match this card to the existing dashboard" with the repo in hand.
• Open ask → ask before building. Example: "prototype my onboarding" needs goals, target audience, and which dimension to diverge on (UX flow vs. visual treatment vs. copy). Resolve those three, then start.

Explore Many Variations

For exploratory or open work, produce 3+ atomic variations across distinct axes, never three tweaks of one idea:

• Vary on different dimensions: layout, color, type treatment, interaction model.
• Deliberately mix safe matches with at least one novel direction — do not converge early.
• Order them basic → advanced so the reviewer can scan the gradient (the "Design It Twice" premise extended past two).

Match Existing Vocabulary

When editing a live UI, conform to it instead of imposing a new style:

• Reverse-engineer the palette, interactive states (hover/active/disabled), motion timing, and shadow/card/density treatment.
• Match the copy tone too — terse product UI and chatty marketing copy are different vocabularies.
• A change that introduces a foreign style is a regression even when it looks good in isolation.

No-Filler Content

• Every element earns its place. No dummy stats, decorative sections, or lorem blocks added just to fill space. If a block has no purpose, cut it.
• Honest placeholder beats a bad fake. A labeled placeholder ("[product screenshot]") is better than an invented icon or hand-drawn fake image. Do NOT fabricate assets — ask for the real ones.

Animation Decision Framework

Frequency determines approach

Never animate keyboard-initiated actions — they repeat hundreds of times daily, making animation feel sluggish.

Purpose validation

Every animation requires justification: spatial consistency, state indication, explanation, user feedback, or preventing jarring transitions. "It looks cool" alone disqualifies frequent interactions.

Easing rules

Critical: Abandon default CSS easings. Use custom curves:

/* Punchy entrance */
transition-timing-function: cubic-bezier(0.23, 1, 0.32, 1);

Never use ease-in — it delays initial movement exactly when attention peaks, making interfaces feel sluggish.