Fantastic Ui

Fantastic UI — instrument-grade marketing pages and product surfaces

The core idea

A marketing page for a serious product should feel like holding the instrument, not reading a brochure about it. Most landing pages fail because they dress the product in someone else's clothes: gradient blobs, stock screenshots in tilted browser frames, three-column feature grids with icon libraries. The methodology here inverts that: take the product's own visual language (its data, its density, its color logic) and elevate it to editorial quality. The visitor should feel they've already started using the product by the time they reach the CTA.

This is a flexible skill: adapt the principles to the product's actual character. The worked example is a dark finance terminal, but the discipline (one accent, semantic color, live proof, performance and accessibility gates) transfers to any product that has real data or real behavior to show.

The same philosophy applies inside the product: app pages, dashboards, panels, and subpanels are instruments too, and they fail the same way (uniform card grids, decorative color, shadow soup, default focus rings). For marketing pages, follow the five disciplines and page rhythm below. For modifying existing product surfaces, start at [Applying the disciplines to product surfaces](#applying-the-disciplines-to-product-surfaces-pages-panels-subpanels) — the disciplines are the same; the procedure and anatomy differ.

Step 0 — Write the one-sentence brief first

Before any code, commit to a named direction in one sentence. Example from the worked case:

> "Dark, instrument-grade market terminal elevated to editorial: warm-charcoal > ground, single sodium-amber accent, teal/red only as semantic signal colors, > humanist serif display over monospace data."

Every later decision gets tested against this sentence. If you can't write it, you don't have a direction yet — interrogate the product first: What does it actually look like in use? What's its most impressive live behavior? What color already means something in it? A vague brief ("clean, modern") produces template output; a specific one produces a point of view.

The five disciplines

1. Single-accent color system

Build the palette as a scale from one ground hue, with exactly one accent and a small set of semantic colors that are never used decoratively:

• Ground scale — 4–5 steps of near-black tinted *toward the accent's

warmth* (e.g. warm charcoal #0b0b0a → panel #151309), so even empty space carries the direction.

• Hairlines, not shadows — 1px borders from the ground scale

(--hair, --hair-lit) define surfaces. Dark UIs read cheap when they lean on drop shadows.

• Ink scale — 3 steps of off-white text tinted the same direction

(--ink, --ink-2, --muted). Pure #fff on near-black glares.

• One accent + one highlight of it (--sodium: #f2a83c,

--sodium-hi: #ffc164). The accent marks what matters: eyebrows, CTAs, focus rings, the brand mark, selection color. If it's everywhere, it's nowhere.

• Semantic colors stay semantic — if the domain has meaning-colors (up

teal / down red, pass green / fail red), they appear only with that meaning, never as decoration. This is what makes a page feel like an instrument: color is information.

Define all of it as CSS custom properties on the page root so the direction is auditable in one place. Full token block in [references/css-architecture.md](references/css-architecture.md).

2. Three-face typography, zero webfonts

Pair three type roles using system font stacks only — no font requests, no FOUT, no layout shift:

• Display serif for headlines — a humanist serif stack

("Iowan Old Style", "Palatino Linotype", Palatino, ui-serif, Georgia) gives editorial gravity that default sans headlines can't. text-wrap: balance, tight letter-spacing, clamp() sizing, an italic `` in the accent-highlight color for the one word that matters.

• Monospace for data, eyebrows, buttons, microcopy — with

font-variant-numeric: tabular-nums. Mono is what makes numbers feel measured rather than claimed. Eyebrow kickers: mono, uppercase, ~0.22em tracking, accent color, a short rule-line before the text.

• System sans for body prose.

The serif/mono contrast does the aesthetic work that webfonts usually get hired for, at zero performance cost.

3. Live proof over screenshots

The hero visual should be the product actually running, drawn on a `` — not a screenshot, not a stock illustration. A screenshot says "trust us"; a live rendering says "look at it go". Simulated data is fine (random walks tuned to look plausible); the honesty is in the mechanics being real.

Non-negotiables for any canvas animation (full annotated pattern in [references/canvas-hero.md](references/canvas-hero.md)):

• DPR-aware sizing, capped at 2, re-applied on resize
• Pause via visibilitychange when the tab is hidden
• prefers-reduced-motion renders one static frame — same composition,

no loop

• Full effect cleanup: cancel RAF, remove every listener
• Colors pulled from the same palette tokens as the CSS

Smaller instances of the same idea (sparklines painted into feature cards) make the whole page feel alive without any animation library.

4. Page rhythm — dense, alternating, specific

Structure the page as alternating texture bands rather than uniform sections. The worked skeleton, generalizable:

1. Sticky nav — transparent until scrolled, then blur + hairline
2. Hero — copy left, live canvas right; trust stats under the CTA
3. Stat tape — a slow marquee of real numbers (with an srOnly static

list for screen readers, marquee aria-hidden)

1. Thesis explainer — diagram + editorial copy; teach the product's core

mental model in one section

1. Feature bento — asymmetric grid (3+3 / 2+2+2 columns, 6→2→1

responsive), each card carrying a proof artifact (sparkline, pill row, mini-table), never an icon

1. Atmosphere band — full-bleed section over a subtle AI-generated

background (see [references/ai-atmosphere.md](references/ai-atmosphere.md)) carrying the accountability/credibility content

1. Interactive toggle section — one real state switch (markets, plans,

platforms) with proper ARIA tabs, proving the page is an application

1. Principles trio — the "why trust us" values, stated plainly
2. Final CTA + honest fine print

Copywriting voice: numbers are the protagonists (5,000+ tickers, ±70 mints a call); microcopy in monospace reads like terminal output; fine print is honest ("Not investment advice · Track record is paper trading") — candor is a premium signal. Headlines state a thesis, not a feature list ("The market is always in rotation. See it turn first.").

5. Performance and accessibility as gates, not polish

These are pass/fail, checked before shipping:

Performance

• Zero webfonts, zero animation/UI libraries — the page needs only the

framework it lives in

• Any raster asset ≤ ~30 KB (generate large, compress hard to webp)
• Motion on compositor properties only (transform, opacity); scroll work

via IntersectionObserver, never scroll handlers doing layout reads

• Explicit dimensions on media; hero canvas gets width/height attributes

Accessibility

• Every animation (canvas, reveals, marquee, pulse) gated behind

prefers-reduced-motion — reveals appear instantly, canvas draws one frame

• Skip link as the first focusable element
• A shared .focusable class: `outline: 2px solid var(--accent);

outline-offset: 3px on :focus-visible` — designed focus, not default

• Real ARIA on interactive widgets (role="tablist" / aria-selected on

toggles); decorative canvases aria-hidden="true"

• Marquee/ticker content duplicated in a visually-hidden static list
• Semantic landmarks: nav, header, section with ids, footer

Applying the disciplines to product surfaces (pages, panels, subpanels)

Same five disciplines, two shifts in how they're applied. Full procedure, panel anatomy, and state patterns: [references/product-surfaces.md](references/product-surfaces.md) — read it before touching any app page or panel.

Shift 1 — the brief and the tokens belong to the app, not the page. A marketing page can own its look; product surfaces can't, or the app becomes a costume party. Write ONE one-sentence brief for the whole application, lift the token block to the app shell (:root or the app's root class), and forbid page-local color definitions. Every page, panel, and subpanel draws from the same ground scale, ink scale, one accent, and semantic set. A panel that needs "its own color" is almost always misusing decoration where it needs hierarchy.

Shift 2 — rhythm becomes hierarchy. A landing page alternates texture bands to keep a scrolling reader engaged; an app screen is operated, so composition follows attention instead: summary before detail, primary panel visibly primary (span, position, density — not louder color), and nesting depth encoded by the ground scale (each subpanel level exactly one ground step lighter, hairline-separated — never stacked shadows, max ~3 levels).

Retrofit procedure for existing screens (details in the reference):

1. Audit — inventory every page/panel/subpanel; screenshot before;

extract every color, face, radius, and shadow in use. The audit usually finds 30+ greys and 3 accents; the target is one scale and one accent.

1. Brief — one sentence for the whole app, tested against real screens.
2. Tokens first — install the shared token block and map old values to

tokens without redesigning anything yet. This is the mechanical commit.

1. Primitives second — build the shared panel/eyebrow/stat/table/state

primitives once, from the tokens.

1. Migrate surface by surface — highest-traffic screen first, one PR per

screen, information identical, presentation rebuilt from primitives. Never fork a token locally to "match the old look".

1. Consistency gate — cross-screen pass at the end: same accent meaning,

same focus ring, same panel anatomy everywhere; grep for hex literals outside the token file (there should be none).

The accessibility phase — check and fix (WCAG 2.2 AA)

Discipline 5 states the gates; this phase is how you actually pass them. It is a required workflow phase, not an optional polish step — run it on every build and on every retrofitted screen. Full audit procedure, contrast math, manual pass scripts, and fix patterns: [references/wcag-audit.md](references/wcag-audit.md) — read it when you enter this phase.

The phase runs at three moments:

1. Token time — validate contrast once, inherit it everywhere. Before

any component is styled, compute the contrast matrix for every ink×ground and accent×ground token pair (script in the reference). Every text token must clear 4.5:1 on every ground step it will sit on (3:1 for large text); accent-as-UI-component and focus rings must clear 3:1 against adjacent colors. Fixing a failing pair means adjusting the token, never a local override — one fix repairs every screen at once. Record the passing matrix as a comment in the token file.

1. Build time — semantics as you go. Landmarks, heading order, real

ARIA on widgets, canvas/marquee alternatives, labels on every input — cheaper to build in than to bolt on (patterns in the reference).

1. Pre-ship — audit, fix, re-audit. Automated sweep (axe-core with

WCAG 2.2 AA tags + Lighthouse a11y) plus the four manual passes no tool can do: keyboard traversal, screen-reader walkthrough, reduced-motion toggle, and 320 px / 200 % zoom reflow. Triage: axe critical/serious findings and any manual-pass failure are ship blockers; moderates are fixed or explicitly documented; minors go to the backlog. Fix, then re-run to zero blockers — an audit without the re-run is theater.

Two rules that keep fixes on-system:

• Fix at the highest level possible. Token > primitive > component >

instance. A contrast failure fixed on one card will recur on the next screen; fixed in the token it can never recur.

• Accessibility fixes must not fork the design. If a fix seems to

require a new color or a louder style, re-read the failing criterion — the compliant answer is almost always within the system (a lighter ink step, a thicker hairline, a visible focus ring from the existing accent).

CSS architecture

Use a CSS module (or equivalent scoping) with every rule scoped under the page root class — no bare element selectors that leak into the rest of the app. For a single marketing page, tokens live on .page; for product surfaces, tokens are promoted to the app shell and pages scope only their layout rules. Shared primitives (.wrap, .eyebrow, .btn, .mono, .focusable, .srOnly, and for apps .panel, .panelHead, .stat) compose via multiple classes. Reveal-on-scroll is one [data-reveal] attribute + an isIn class toggled by a single IntersectionObserver. Full patterns and the token block: [references/css-architecture.md](references/css-architecture.md).

Ship checklist

Run through this before calling the page done:

• [ ] The one-sentence brief still describes the shipped page
• [ ] One accent color; semantic colors appear only with their meaning
• [ ] No webfonts, no new dependencies, assets ≤ 30 KB each
• [ ] Hero shows the product running, not a picture of it
• [ ] prefers-reduced-motion: every animation has a static path (verify by

toggling the OS setting or DevTools emulation)

• [ ] Keyboard pass: skip link, visible focus rings, tabs operable
• [ ] Responsive pass at 320 / 768 / 1024 / 1440 — bento collapses cleanly,

no horizontal overflow

• [ ] Tab-hidden pass: canvas RAF actually stops (check via Performance panel)
• [ ] Copy pass: numbers concrete, fine print honest, zero hype adjectives

("revolutionary", "powerful", "seamless" are banned)

• [ ] Accessibility phase completed: token contrast matrix validated,

axe-core (wcag2a/wcag2aa/wcag22aa tags) at zero critical/serious, keyboard + screen-reader + reduced-motion + reflow manual passes done, findings fixed and re-audited (see references/wcag-audit.md)

Additional gates when the work touched product surfaces:

• [ ] No hex/rgb literals outside the token file (grep proves it)
• [ ] Every panel uses the shared anatomy (eyebrow header, hairline

separation, actions right) — no one-off panel styles

• [ ] Subpanel nesting encoded by ground-scale steps, ≤ 3 levels, no

stacked shadows

• [ ] Empty, loading, and error states designed for every migrated panel

(skeletons on ground scale, semantic color only on real errors)

• [ ] Cross-screen pass: accent means the same thing on every page; focus

rings identical; density comparable between sibling panels

• [ ] Before/after screenshots captured for each migrated screen

References

• [references/css-architecture.md](references/css-architecture.md) — the full

token system, scoping rules, shared primitives, and responsive patterns. Read when writing the stylesheet.

• [references/canvas-hero.md](references/canvas-hero.md) — annotated live

canvas hero + sparkline + scroll-reveal code with all lifecycle handling. Read when building any canvas or reveal behavior.

• [references/ai-atmosphere.md](references/ai-atmosphere.md) — generating and

compressing AI atmosphere backgrounds (prompt recipe + pipeline script). Read when a section needs an atmospheric background image.

• [references/product-surfaces.md](references/product-surfaces.md) — the full

retrofit procedure for existing app pages, panel and subpanel anatomy, nesting/depth rules, state design (empty/loading/error), and density guidance. Read whenever modifying or restyling i

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Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: succtorlin
• Source: succtorlin/fantastic-ui
• License: MIT

Install and usage instructions live in the source repository linked above.