UI Design

UI Design

A design-quality reference for any visual output you produce. It exists to make that output look like it came from a research desk, not a marketing landing page or a generic AI template.

Read this before producing any styled output — it covers design taste: typography, color, composition, and restraint. The examples below are HTML/CSS (the most common surface), but the principles apply to any visual you render — charts and images, PDFs, on-screen layouts — not just HTML.

This skill exists to help you match the user's personal frontend style and UI preferences — those always win over the defaults below. If the user has stated a taste — in this conversation, in your long-term memory, or in their saved preferences — it outranks every rule here. They want a specific brand color, a chosen font, a different accent, dark-only, no serif? Do that. The directions below are strong defaults for when the user hasn't expressed a preference; they are never a license to overrule the user's explicit style.

These are reference defaults, not a cage. They anchor quality and steer you off generic, lazy output — they don't replace your own judgment. When you have a clearly better, coherent choice for the specific content, take it. The only non-negotiables are the hard constraints: WCAG AA contrast, green/red reserved for profit/loss, and the theme-variable + print mechanics. The specific palette, font pairings, and exact scale below are strong starting points you are free to improve on.

The Tone: Research Desk, Not Marketing Page

The audience is a portfolio manager, analyst, or sophisticated investor reading a research note. They want dense, scannable, credible information design — the visual language of a sell-side note, a Bloomberg terminal, or a quality print newspaper's business section. Not a SaaS hero page.

This means:

• Information density over whitespace theatre. A research reader expects a high signal-per-screen ratio.
• Restraint over decoration. No hero gradients, no oversized rounded cards floating on pastel backgrounds, no "Get Started" energy.
• Numbers are the protagonist. Tables, figures, and charts carry the page; prose supports them.
• Credibility cues: sources cited, dates stamped, units labelled, precision consistent.

Avoid AI Slop

These are the tells of generic AI-generated UI. Each one has a concrete replacement — use the "instead" column.

Typography

Commit to an intentional pairing — a real headline voice plus a clean body face, loaded from the Google Fonts CDN (allowlisted). The three below are proven starting points: pick one, use the user's brand font, or choose your own with the same level of intent. What matters is the commitment — don't fall back to Inter-everywhere or the bare system stack.

Pairings that work (starting points)

1. Editorial / authoritative — headings "Source Serif 4", Georgia, serif; body "Inter", -apple-system, sans-serif. Serif headings give a print-research feel; body stays clean and readable. (The only acceptable use of Inter: as the body of a serif-headed document — never as the headline voice.)
2. Modern terminal — headings & body "IBM Plex Sans", system-ui, sans-serif; figures/tables "IBM Plex Mono", monospace. Plex reads as engineered and precise; the mono companion makes numeric tables align beautifully.
3. Refined grotesque — headings "Newsreader", Georgia, serif (a true reading serif) or "Libre Franklin", sans-serif; body "Libre Franklin", sans-serif. Franklin is a workhorse news face with more character than Inter.

<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
<link href="https://fonts.googleapis.com/css2?family=Source+Serif+4:opsz,wght@8..60,400;8..60,600&family=Inter:wght@400;500;600&display=swap" rel="stylesheet">

Type scale

A real, restrained scale (ratio ~1.25) keeps sizing coherent. The values below are a sensible default — whatever scale you use, keep it consistent rather than sizing ad-hoc.

--text-xs: 0.75rem;   /* 12px — captions, source lines, table headers */
--text-sm: 0.875rem;  /* 14px — secondary text, dense table cells */
--text-base: 1rem;    /* 16px — body */
--text-lg: 1.25rem;   /* 20px — section headings (h2/h3) */
--text-xl: 1.75rem;   /* 28px — KPI figures */
--text-2xl: 2.25rem;  /* 36px — page title (h1); typically one per document */

Numbers

Financial figures must use tabular (monospaced) digits so columns align and numbers don't jitter when they update:

.figure, td.num, .kpi-value {
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum" 1;
}

Right-align numeric table columns. Keep decimal precision consistent within a column (e.g. all prices to 2dp). Label units once in the header, not on every cell.

Color

A restrained, committed palette: ink on paper with a single accent, plus the two semantic financial colors. One accent is the disciplined default — add a second hue only when it genuinely earns its place (a deliberate two-tone scheme), never as rainbow filler. The table below is a reference palette that meets AA on its paired backgrounds; use it, or derive your own that holds the same constraints.

Rules:

• WCAG AA: body text ≥ 4.5:1 against its background; large text/UI ≥ 3:1. The values above meet AA on their paired backgrounds. Verify any custom pairing.
• Green/red are reserved for profit/loss and beat/miss. Never use them as decorative categorical colors.
• Dark-aware via the fallback pattern: author every color as var(--color-role, #literalFallback) so the output themes with the app yet still renders standalone and in print.
• Categorical chart palette (when you genuinely need categories): derive 3-4 muted tints rather than full-saturation hues, e.g. the accent plus two desaturated neighbors. More than 4 series → switch to small multiples or a table.

Composition

• One reading column, left-aligned, max-width ~`min(100%, 1100px)` for reading-heavy layouts (wider for dense, data-heavy views). Center the column on the page, not the text within it.
• Hairline rules over boxes to divide sections. A 1px top border on each section header carries hierarchy more cleanly than wrapping everything in shadowed cards.
• A real grid for KPI rows: display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: .... Consistent gaps; aligned baselines.
• Generous but consistent vertical rhythm between sections; tight, dense rhythm inside tables. Density is a feature for data; air is for separating ideas.
• Hierarchy through weight and size, not color. A heading is bigger/heavier, not a different hue. Reserve color for semantics (links, profit/loss).
• Tables earn their space: zebra striping is optional and should be subtle (a 2-3% tint); a hairline under the header row and between groups is usually enough. Right-align numbers, left-align labels.

Motion (Restrained)

Motion is the exception, not the rule, in a research document.

• Keep motion restrained and purposeful — a brief entrance (e.g. a staggered fade-in of sections on load) is plenty. Avoid scattered hover wiggles, parallax, and infinite loops in a report.
• Charts may animate their initial draw (Chart.js/ECharts default) — keep it short.
• Respect reduced-motion and never let animation block print:

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
}
@media print {
  *, *::before, *::after { animation: none !important; transition: none !important; opacity: 1 !important; }
}

(The opacity: 1 !important in the @media print block above is what keeps entrance-animated elements from exporting blank — keep it.)

Match Complexity to the Content

Spend effort on precision, number formatting, alignment, and sourcing — not decoration. Add visual complexity only when the content genuinely calls for it; a clean, dense research note beats an over-animated one.

Apply Checklist

Before delivering any styled output:

• Committed to one typographic pairing from above (no Inter-as-headline, no system-font-only)
• Real type scale used — no ad-hoc font sizes
• Financial figures use font-variant-numeric: tabular-nums; numeric columns right-aligned, consistent precision
• One accent color; green/red reserved strictly for profit/loss
• All colors authored as var(--color-role, #fallback); WCAG AA verified for body text
• No purple gradients, no uniform shadowed-card grids, no emoji icons, no rainbow charts
• Left-aligned reading column, hairline rules over boxes, consistent vertical rhythm
• Motion (if any) respects prefers-reduced-motion and is forced off / opacity-restored in @media print
• Reads as a research desk artifact, not a marketing page — dense, credible, scannable