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Guide for creating distinctive, production-grade frontend interfaces. Covers visual design systems, typography, color, motion, spatial composition, and web interface standards. Use when designing UI, establishing design systems, or reviewing visual quality of frontend code.
npx skill4agent add s-hiraoku/synapse-a2a frontend-design/* BAD: Generic, seen everywhere */
font-family: 'Inter', 'Roboto', 'Arial', sans-serif;
/* GOOD: Distinctive and paired intentionally */
--font-display: 'Instrument Serif', serif; /* headings */
--font-body: 'Satoshi', sans-serif; /* body text */
--font-mono: 'Berkeley Mono', monospace; /* code *//* Tabular numbers for aligned columns */
.data-cell { font-variant-numeric: tabular-nums; }
/* Balanced headings prevent widow words */
h1, h2, h3 { text-wrap: balance; }
/* Proper ellipsis character */
.truncate::after { content: '\2026'; } /* … not ... *//* Single line truncation */
.truncate { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
/* Multi-line clamping */
.clamp-3 { display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical; overflow: hidden; }
/* Flex children need min-w-0 for truncation to work */
.flex-child { min-width: 0; }:root {
/* Primitives */
--gray-50: oklch(0.98 0.005 240);
--gray-900: oklch(0.15 0.01 240);
--accent: oklch(0.65 0.25 30);
/* Semantic tokens */
--color-bg: var(--gray-50);
--color-text: var(--gray-900);
--color-text-muted: oklch(0.55 0.01 240);
--color-border: oklch(0.88 0.005 240);
--color-accent: var(--accent);
--color-accent-hover: oklch(0.58 0.28 30);
}
@media (prefers-color-scheme: dark) {
:root {
--color-bg: var(--gray-900);
--color-text: var(--gray-50);
--color-text-muted: oklch(0.65 0.01 240);
--color-border: oklch(0.28 0.005 240);
}
}prefers-reduced-motiontransformopacitytransition: all/* GOOD: Specific properties, respects user preference */
.card {
transition: transform 200ms ease-out, opacity 150ms ease-out;
}
@media (prefers-reduced-motion: reduce) {
.card { transition: none; }
}/* Fluid typography */
h1 { font-size: clamp(2rem, 5vw, 4rem); }
/* Container queries for component-level responsiveness */
.card-container { container-type: inline-size; }
@container (min-width: 400px) {
.card { grid-template-columns: 200px 1fr; }
}/* Noise texture overlay */
.surface::after {
content: '';
position: absolute;
inset: 0;
background: url('/noise.svg');
opacity: 0.03;
pointer-events: none;
}
/* Gradient mesh */
.hero {
background:
radial-gradient(ellipse at 20% 50%, oklch(0.7 0.15 250 / 0.3), transparent 50%),
radial-gradient(ellipse at 80% 20%, oklch(0.7 0.2 30 / 0.2), transparent 50%),
var(--color-bg);
}// Explicit dimensions prevent layout shift
<Image src={src} width={800} height={600} alt="Description" />
// Below-fold: lazy load
<Image src={src} loading="lazy" alt="..." />
// Above-fold: prioritize
<Image src={src} priority alt="..." />
// Decorative: empty alt
<Image src={pattern} alt="" aria-hidden="true" />| State | Treatment |
|---|---|
| Default | Base appearance |
| Hover | Increased contrast or subtle shift |
| Focus | Visible ring via |
| Active/Pressed | Slight scale or color change |
| Disabled | Reduced opacity + |
.button {
background: var(--color-accent);
transition: background 150ms ease-out, transform 100ms ease-out;
}
.button:hover { background: var(--color-accent-hover); }
.button:focus-visible { outline: 2px solid var(--color-accent); outline-offset: 2px; }
.button:active { transform: scale(0.98); }| Avoid | Instead |
|---|---|
| Inter/Roboto/Arial everywhere | Choose distinctive, project-appropriate typefaces |
| Purple gradient on white | Commit to a specific, cohesive palette |
| Uniform card grids | Vary sizes, add featured/hero cards |
| Shadows on everything | Use shadow purposefully for elevation hierarchy |
| Match radius to content type and context |
| Identical hover effects | Tailor interaction feedback to element function |