UI Design Patterns

Before You Start: Load Design Context

1. Read .agents/design-context.md (written by the design-context skill). If it is missing, look for tokens in tailwind.config.* or :root CSS variables. If nothing exists, use the defaults (Primary #2563EB, Secondary #7C3AED, Accent #F59E0B, Tailwind gray neutrals, Inter for headings and body, Minimal style) and tell the user defaults were used — suggest running design-context.
2. Map tokens to CSS variables once, then use only the variables: --color-primary, --color-primary-light, --color-primary-dark, --color-secondary, --color-accent, --color-neutral-50…--color-neutral-900, --color-success/-warning/-error, --font-heading, --font-body, --font-mono, --radius, and the 4px-base spacing scale.
3. Tailwind: expose the same variables (v3 theme.extend, v4 @theme) as primary, primary-light, primary-dark, secondary, accent, neutral-*, font-heading, font-body. The indigo-* / gray-* classes in the examples below are placeholders for these tokens.
4. Figma: if the user gives a Figma URL, pull it with the Figma MCP (get_design_context, get_screenshot) and match it; it overrides the context file for that design.
5. Let the style archetype set radius, shadow depth, and how much of section 9 (trends) to use — Minimal and Corporate use none of it.

1. Component Design Principles (Atomic Design)

Build UI in layers. Never start with a full page — start with the smallest pieces.

Hierarchy

1. Tokens — colors, spacing, radii, shadows, typography scale
2. Atoms — button, input, badge, avatar, icon
3. Molecules — search bar (input + button), form field (label + input + error), card header (avatar + name + timestamp)
4. Organisms — navigation bar, hero section, comment thread, pricing table
5. Templates — page layouts composed of organisms
6. Pages — templates with real data

Rules

• Every component gets its own set of CSS custom properties scoped to its root.
• Prefer composition over configuration. A Card with children beats a Card with 15 props.
• Components should be stateless by default. Lift state up.

/* Token layer — values come from .agents/design-context.md (defaults shown) */
:root {
  --color-primary: #2563EB;
  --color-surface: #FFFFFF;
  --radius-md: 0.75rem;
  --shadow-sm: 0 1px 2px oklch(0% 0 0 / 0.05);
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-12: 3rem;
  --space-16: 4rem;
}

Canonical spacing scale (all UI skills): 4px base — 4, 8, 12, 16, 24, 32, 48, 64px (Tailwind 1, 2, 3, 4, 6, 8, 12, 16). Don't use off-scale values.

2. Visual Hierarchy Framework

Control where the eye goes. Rank every element by importance and apply these levers:

The Squint Test

Blur your eyes or zoom out to 25%. If you can still identify the primary action and main heading, your hierarchy works.

Tailwind Implementation

<!-- High emphasis -->
<h1 class="text-4xl font-extrabold tracking-tight text-gray-950">
  Ship faster with AI
</h1>

<!-- Medium emphasis -->
<p class="mt-4 text-lg text-gray-600 max-w-2xl">
  Build production-ready components in minutes, not hours.
</p>

<!-- Low emphasis -->
<span class="text-xs text-gray-500 uppercase tracking-wide">
  Updated 2 hours ago
</span>

3. Interactive States

Every interactive element needs all five states. No exceptions.

State Definitions

.btn-primary {
  /* Default */
  background: var(--color-primary);
  color: white;
  border-radius: var(--radius-md);
  padding: var(--space-2) var(--space-4);
  font-weight: 600;
  transition: background-color 150ms ease, box-shadow 150ms ease, transform 150ms ease, filter 150ms ease;

  /* Hover — subtle lift or brightness shift */
  &:hover {
    filter: brightness(1.1);
    box-shadow: 0 4px 12px oklch(0% 0 0 / 0.15);
    transform: translateY(-1px);
  }

  /* Active — pressed feel */
  &:active {
    transform: translateY(0);
    filter: brightness(0.95);
    box-shadow: var(--shadow-sm);
  }

  /* Focus — visible ring for keyboard users */
  &:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
  }

  /* Disabled — dimmed, no hover/active effects (don't add pointer-events: none — it hides the not-allowed cursor) */
  &:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
    filter: none;
  }
}

Tailwind Shorthand

<button class="bg-indigo-600 text-white px-4 py-2 rounded-lg font-semibold
  hover:bg-indigo-500 hover:-translate-y-0.5 hover:shadow-lg
  active:translate-y-0 active:bg-indigo-700
  focus-visible:outline focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-indigo-600
  disabled:opacity-50 disabled:cursor-not-allowed disabled:pointer-events-none
  transition-all duration-150">
  Click me
</button>

4. Feedback Patterns

Loading States

• Skeleton screens over spinners. Show the shape of content that's coming.
• Use motion-safe:animate-pulse on placeholder blocks, and mark the region aria-busy="true" with an sr-only "Loading…" label.
• Show loading inline near the action that triggered it.

<!-- Skeleton card -->
<div class="motion-safe:animate-pulse space-y-3" aria-busy="true">
  <span class="sr-only">Loading…</span>
  <div class="h-48 bg-gray-200 rounded-xl"></div>
  <div class="h-4 bg-gray-200 rounded w-3/4"></div>
  <div class="h-4 bg-gray-200 rounded w-1/2"></div>
</div>

Success State

• Green accent, checkmark icon, brief confirmation text.
• Announce it with role="status" (polite live region). Auto-dismiss after 5+ seconds, and never auto-dismiss messages that contain an action.

Error State

• Red accent, descriptive message, recovery action.
• Never just say "Error." Say what went wrong and what to do.
• Don't rely on red alone: pair it with an icon and text; use role="alert" for errors that appear after submit.

Empty State

• Illustration or icon, explanation, primary action to fix it.

<div class="text-center py-16">
  <svg class="mx-auto h-12 w-12 text-gray-400" aria-hidden="true"><!-- inbox icon --></svg>
  <h3 class="mt-4 text-lg font-semibold text-gray-900">No messages yet</h3>
  <p class="mt-2 text-sm text-gray-500">Start a conversation to see messages here.</p>
  <button type="button" class="mt-6 bg-indigo-600 text-white px-4 py-2 rounded-lg">
    New message
  </button>
</div>

5. Navigation Patterns

Sidebar Navigation

• Width: 240–280px desktop, collapsible to 64px (icon-only).
• Group items by category with subtle section headers.
• Active item: filled background, bold text, left accent bar, and aria-current="page".

Top Navigation

• Fixed/sticky at top. Height: 56–64px.
• Logo left, nav links center or left, actions right.
• Mobile: collapse to hamburger at md breakpoint.

Tabs

• Use for switching views within the same context.
• Active tab: bottom border (2–3px) in primary color + bold text. Use role="tablist"/role="tab" with aria-selected and arrow-key navigation (or plain links if each tab is its own URL).
• Never more than 7 tabs. Use dropdown overflow for more.

Breadcrumbs

• Use / or > separator.
• Current page is not a link, just text.
• Truncate middle items on long paths.

6. Form Design

Rules

1. Labels above inputs — not floating, not inline. Always visible.
2. One column — multi-column forms reduce completion rate.
3. Group related fields with subtle section dividers.
4. Inline validation — validate on blur, not on every keystroke.
5. Error messages below the field, in red, with specific guidance.
6. Primary action left-aligned at form bottom. Secondary action as text link.

<div class="space-y-1.5">
  <label for="email" class="block text-sm font-medium text-gray-700">
    Email address
  </label>
  <input
    type="email"
    id="email"
    class="block w-full rounded-lg border border-gray-300 px-3 py-2
      text-gray-900 placeholder:text-gray-400
      focus:border-indigo-500 focus:ring-2 focus:ring-indigo-500/20
      transition-colors"
    placeholder="you@example.com"
    autocomplete="email"
    aria-describedby="email-error"
  />
  <!-- On error: remove `hidden` and set aria-invalid="true" on the input -->
  <p id="email-error" class="text-sm text-red-600 hidden">Please enter a valid email address.</p>
</div>

7. Accessibility as Design

Accessibility is not an afterthought. It is a design constraint applied from the start.

Contrast

• Normal text: 4.5:1 minimum contrast ratio (WCAG 2.2 AA).
• Large text (≥24px regular, or ≥18.66px bold): 3:1 minimum.
• Non-text UI (input borders, icons, focus rings, chart marks): 3:1 against adjacent colors.
• Placeholder text is not a label and should still meet 4.5:1 if it carries information.
• Use oklch color space for perceptually uniform contrast adjustments.

Focus Indicators

• Never remove outline without replacing it.
• Use focus-visible (not focus) to avoid showing rings on mouse click.
• Ring: 2px solid, offset 2px, primary color, with 3:1 contrast against the background.
• Focused elements must not be hidden behind sticky headers/footers (WCAG 2.4.11) — add scroll-padding-top equal to the header height.

Target Size

• WCAG 2.5.8 (AA): pointer targets at least 24×24 CSS px (or spaced so a 24px circle doesn't overlap a neighbour).
• Platform guidance for touch: 44×44pt (Apple HIG), 48×48dp (Material). Use 44px+ for primary touch targets.

Semantic Structure

• One <h1> per page.
• Headings in order (h1 > h2 > h3). Never skip levels.
• Use <nav>, <main>, <aside>, <footer> landmarks.
• Buttons for actions, links for navigation. Never <div onclick>.
• aria-label on icon-only buttons.

Motion

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

8. Responsive Breakpoint Strategy

Breakpoints (Tailwind defaults — canonical for all UI skills)

Mobile-First Rules

• Start with the mobile layout. Add complexity at larger breakpoints.
• Stack columns on mobile, side-by-side on md+.
• Navigation becomes hamburger below md.
• Font sizes scale up: text-2xl md:text-4xl lg:text-5xl.
• Generous touch padding on mobile: p-4, tighten on desktop: lg:p-2.

Container Queries (Modern CSS)

.card-container {
  container-type: inline-size;
}

@container (min-width: 400px) {
  .card {
    display: grid;
    grid-template-columns: 200px 1fr;
  }
}

9. Modern UI Trends

Glassmorphism

.glass {
  background: oklch(100% 0 0 / 0.1);
  backdrop-filter: blur(16px) saturate(180%);
  border: 1px solid oklch(100% 0 0 / 0.15);
  border-radius: 1rem;
}

Glass only works over a busy background — check text contrast against the lightest area behind it, and give a solid fallback: @supports not (backdrop-filter: blur(1px)) { .glass { background: oklch(20% 0.02 265 / 0.9); } }.

Bento Grid

.bento {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-auto-rows: minmax(200px, auto); /* fixed 200px rows clip long content */
  gap: 1rem;
}
@media (max-width: 767px) { .bento { grid-template-columns: 1fr; } .bento .featured { grid-column: auto; grid-row: auto; } }
.bento .featured {
  grid-column: span 2;
  grid-row: span 2;
}

Aurora / Mesh Gradient Background

.aurora {
  background: linear-gradient(135deg, oklch(85% 0.15 280), oklch(80% 0.2 320), oklch(75% 0.18 200));
  background-size: 400% 400%;
  animation: aurora-shift 8s ease infinite;
}
@keyframes aurora-shift {
  0%, 100% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
}

10. Advanced CSS Techniques

:has() — Parent Selector

/* Highlight form group when input is focused */
.form-group:has(input:focus-visible) {
  background: oklch(97% 0.01 265);
  border-color: var(--color-primary);
}

/* Card changes layout when it contains an image */
.card:has(img) {
  grid-template-rows: 200px 1fr;
}

Subgrid

.card-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}
.card {
  display: grid;
  grid-template-rows: subgrid;
  grid-row: span 3; /* header, body, footer align across cards */
}

Scroll-Driven Animations

/* Progressive enhancement: only where supported and motion is OK */
@supports (animation-timeline: view()) {
  @media (prefers-reduced-motion: no-preference) {
    .fade-in {
      animation: fade-in linear both;
      animation-timeline: view();
      animation-range: entry 0% entry 100%;
    }
  }
}
@keyframes fade-in {
  from { opacity: 0; transform: translateY(2rem); }
  to { opacity: 1; transform: translateY(0); }
}

Verify: Render and Check

Don't hand over code you haven't looked at. After generating it:

1. Screenshot it at mobile and desktop widths, e.g. npx playwright screenshot --full-page --viewport-size=390,844 file://$PWD/index.html mobile.png, then again with --viewport-size=1440,900 (or point at the dev server URL).
2. Open both images and check: no horizontal scroll or clipped/overlapping text, hierarchy reads at a glance, brand tokens are applied, images load at the right aspect ratio.
3. Tab through once: every interactive element gets a visible focus ring, in a logical order.
4. Check every state you built (hover, focus, disabled, loading, empty, error) at least once, and run a contrast check on muted text.
5. Fix what you find and re-screenshot before reporting done.

Quick Reference: Design Checklist

Before shipping any UI component, verify:

• Visual hierarchy is clear (squint test passes)
• All interactive elements have hover, active, focus-visible, and disabled states
• Color contrast meets WCAG 2.2 AA (4.5:1 text, 3:1 large text and UI components)
• Targets are ≥24×24px (44px+ for primary touch targets)
• Rendered and screenshotted at 390px and 1440px (see Verify)
• Focus order is logical (tab through the page)
• Responsive at all breakpoints (320px to 1920px)
• Loading, empty, and error states are designed
• Spacing uses the 4px-base scale (4, 8, 12, 16, 24, 32, 48, 64)
• Typography scale is limited to 4–6 sizes
• Motion respects prefers-reduced-motion
• Semantic HTML is used (landmarks, headings, button vs. link)