Builds production-quality UIs. Use when building or modifying user-facing interfaces. Use when creating components, implementing layouts, managing state, or when the output needs to look and feel production-quality rather than AI-generated.
Builds production-quality UIs. Use when building or modifying user-facing interfaces. Use when creating components, implementing layouts, managing state, or when the output needs to look and feel production-quality rather than AI-generated.
Frontend UI Engineering
Overview
Build production-quality user interfaces that are accessible, performant, and visually polished. The goal is UI that looks like it was built by a design-aware engineer at a top company — not like it was generated by an AI. This means real design system adherence, proper accessibility, thoughtful interaction patterns, and no generic "AI aesthetic."
Before implementing any UI, read $TGD_DIR/<feature-name>/DESIGN.md. The Visual Direction, Anti-patterns, Design Tokens, and Typography Scale sections are the source of truth for all design decisions. This skill covers code architecture, component patterns, state management, and accessibility — not visual design rules.
Local state (useState) → Component-specific UI state
Lifted state → Shared between 2-3 sibling components
Context → Theme, auth, locale (read-heavy, write-rare)
URL state (searchParams) → Filters, pagination, shareable UI state
Server state (React Query, SWR) → Remote data with caching
Global store (Zustand, Redux) → Complex client state shared app-wide
Avoid prop drilling deeper than 3 levels. If you're passing props through components that don't use them, introduce context or restructure the component tree.
Design System Adherence
Avoid the AI Aesthetic
AI-generated UI has recognizable patterns. Avoid all of them:
AI Default
Why It Is a Problem
Production Quality
Purple/indigo everything
Models default to visually "safe" palettes, making every app look identical
Use the project's actual color palette
Excessive gradients
Gradients add visual noise and clash with most design systems
Flat or subtle gradients matching the design system
Rounded everything (rounded-2xl)
Maximum rounding signals "friendly" but ignores the hierarchy of corner radii in real designs
Consistent border-radius from the design system
Generic hero sections
Template-driven layout with no connection to the actual content or user need
Content-first layouts
Lorem ipsum-style copy
Placeholder text hides layout problems that real content reveals (length, wrapping, overflow)
Realistic placeholder content
Oversized padding everywhere
Equal generous padding destroys visual hierarchy and wastes screen space
Consistent spacing scale
Stock card grids
Uniform grids are a layout shortcut that ignores information priority and scanning patterns
Purpose-driven layouts
Shadow-heavy design
Layered shadows add depth that competes with content and slows rendering on low-end devices
Subtle or no shadows unless the design system specifies
Spacing and Layout
Use a consistent spacing scale. Don't invent values:
/* Use the scale: 0.25rem increments (or whatever the project uses) *//* Good */padding: 1rem; /* 16px *//* Good */gap: 0.75rem; /* 12px *//* Bad */padding: 13px; /* Not on any scale *//* Bad */margin-top: 2.3rem; /* Not on any scale */
Typography
Respect the type hierarchy:
h1 → Page title (one per page)
h2 → Section title
h3 → Subsection title
body → Default text
small → Secondary/helper text
Don't skip heading levels. Don't use heading styles for non-heading content.
Color
Use semantic color tokens: text-primary, bg-surface, border-default — not raw hex values
Ensure sufficient contrast (4.5:1 for normal text, 3:1 for large text)
Don't rely solely on color to convey information (use icons, text, or patterns too)
Accessibility (WCAG 2.1 AA)
Every component must meet these standards:
Keyboard Navigation
// Every interactive element must be keyboard accessible
<button onClick={handleClick}>Click me</button> // ✓ Focusable by default
<div onClick={handleClick}>Click me</div> // ✗ Not focusable
<div role="button" tabIndex={0} onClick={handleClick} // ✓ But prefer <button>
onKeyDown={e => {
if (e.key === 'Enter') handleClick();
if (e.key === ' ') e.preventDefault();
}}
onKeyUp={e => {
if (e.key === ' ') handleClick();
}}>
Click me
</div>
ARIA Labels
// Label interactive elements that lack visible text
<button aria-label="Close dialog"><XIcon /></button>
// Label form inputs<labelhtmlFor="email">Email</label><inputid="email"type="email" />// Or use aria-label when no visible label exists<inputaria-label="Search tasks"type="search" />
