Frontend ui

Frontend UI Engineering

Overview

Build UIs that read as hand-crafted production work, not machine output. The failure mode is the generic "AI aesthetic": default palettes, oversized cards, template layouts with no tie to the content. Conform to the project's real design system, meet WCAG 2.1 AA, and handle every interaction state.

When to Use

• Building new UI components or pages
• Modifying existing user-facing interfaces
• Implementing responsive layouts
• Adding interactivity or state management
• Fixing visual or UX issues

State Management

The narrowest-to-widest state category table (local, lifted, context, URL, server, global store) and the prop-drilling guard live in references/state-management.md — read it when the task adds or changes component state; skip it for pure styling, accessibility, or layout-only changes.

Design System Adherence

Take the spacing scale, type hierarchy, and semantic color tokens from references/design-system.md. Never invent values the project's system does not define.

Avoid the AI Aesthetic

Machine-generated UI has recognizable tells. Reject each:

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

Accessibility (WCAG 2.1 AA)

Every component meets these standards. Use the native element first; reach for ARIA only when no native element fits. Detailed WCAG checks and testing tools are in references/accessibility-checklist.md; working code for keyboard navigation, ARIA labels, focus management, and empty/error states is in references/accessibility-patterns.md.

Reference materials

Where these references show component code, they pair a JavaScript component framework (React) with a server-rendered template stack (Django/Python); CSS and HTML examples are framework-neutral. The patterns hold across frameworks. Apply the equivalent in whatever stack the project uses.

• references/component-architecture.md: file colocation, composition over configuration, and separating data from presentation.
• references/design-system.md: the spacing scale, type hierarchy, and semantic color tokens.
• references/state-management.md: the narrowest-to-widest state category table and the prop-drilling guard.
• references/accessibility-patterns.md: keyboard navigation, ARIA labels, focus management, and empty/error states.
• references/accessibility-checklist.md: WCAG 2.1 AA checks and the tools that verify them.
• references/responsive-and-loading.md: mobile-first breakpoints, skeletons, and optimistic updates with rollback.

Common Rationalizations

Rationalization	Reality
"Accessibility is a nice-to-have"	It's a legal requirement in many jurisdictions and an engineering quality standard.
"We'll make it responsive later"	Retrofitting responsive design is 3x harder than building it from the start.
"The design isn't final, so I'll skip styling"	Use the design system defaults. Unstyled UI creates a broken first impression for reviewers.
"This is just a prototype"	Prototypes become production code. Build the foundation right.
"The AI aesthetic is fine for now"	It signals low quality. Use the project's actual design system from the start.

Red Flags

• Components with more than 200 lines (split them)
• Color as the sole indicator of state (red/green without text or icons)

Verification

After building UI:

• Component renders without console errors
• All interactive elements are keyboard accessible (Tab through the page)
• Screen reader can convey the page's content and structure
• Responsive: works at 320px, 768px, 1024px, 1440px
• Loading, error, and empty states all handled
• Follows the project's design system (spacing, colors, typography)
• No accessibility warnings in dev tools or axe-core