(the visual face). At rest // every course's article is exactly its own GAUGE tall — courses are laid // edge to edge with no overlap, so the wall never needs a clip-path to hide // the covered nine-tenths of each slate: it simply never paints it. Lifting // a slate grows that one article, and only that one, from gauge to its true // height and raises it above its neighbours (z-index), which is what reveals // the rest of the quote and is also the only thing that ever overlaps in // this layout. The quote text itself is never display:none at any height — // the SHORT box just clips it, so a screen reader, Ctrl-F and text selection // still reach the full sentence whether or not it is currently showing. // // Reading a slate rotates it about its NAIL LINE (18px below its head, i.e. // near-top) to -34deg on an underdamped spring (k=210, c=19 — the spec's own // physical numbers, not a hand-tuned easing curve), which is what produces // both the fixed -34deg rest angle AND the single ~3deg overshoot as an // emergent property of the spring rather than a hardcoded keyframe list; the // same spring relaxes back to 0 on release, so "lift" and "return" are one // mechanism read in two directions. Only one slate is ever lifted — lifting // a second sets both aria-expanded values in the same state commit. // // TWO unforced processes keep the wall alive at rest without the wall's own // layout ever moving (BUILDER's alive-at-rest test, and DECISIONS D3's ban on // a moving band leaving its wake as a dead still image, though this // component's band is a light/wind field over a STATIC lattice rather than a // process it matures, so there is no "mature region" to freeze): // 1. An idle gust 190px wide sweeps left-to-right on a 4.8s loop. A // deterministic 3-in-17 subset of slates is centre-nailed; whenever a // centre-nailed slate's tail sits inside the gust it lifts 2.5-5px on // its own short underdamped spring and clatters back. // 2. A light azimuth swings +-14deg on a 22s cosine. It never touches any // slate's own face luminance — only the length and side of the cast // shadow at the top of the course below, via ONE root-level CSS custom // property every slate's box-shadow reads, so the whole wall's relief // inverts together without touching N individual DOM nodes per frame. // --------------------------------------------------------------------------- export interface SlateTestimonial { id: string; quote: string; name: string; role: string; } export interface SlateGaugeProps { /** Testimonials, filled row-major (course 1 left-to-right, then course 2, ...). */ items?: SlateTestimonial[]; /** Slates per course. @default 3 */ columns?: number; /** Heading rendered above the wall. */ heading?: string; className?: string; } // ---- geometry: exactly the spec's course table --------------------------- // gauge = (h - LAP - HEAD) / 2, diminishing ~0.915x per course. const LAP = 20; const HEAD = 8; const COURSE_H = [132, 120, 110, 101, 94]; // Type metrics, in the same unscaled design units as the course table — the // quote is rendered at FONT_PX * scale with LINE_RATIO leading and PAD_Y * // scale of padding, so a course's exposure can be expressed here once and // then simply multiplied by the fit scale like every other box dimension. const FONT_PX = 10; const LINE_RATIO = 1.36; const LINE_PX = FONT_PX * LINE_RATIO; const PAD_Y = 6; // A course's EXPOSURE is its computed gauge quantised down to a whole number // of text lines. The gauge is what the slater derives; the quantisation is // what stops the lap from falling through the middle of a line of type, which // is the difference between reading as a slate lapping its neighbour and // reading as a sentence that got cut off. function exposureFor(gauge: number): number { // Only the HEAD padding is inside the exposure. Counting the foot padding // too left exactly one padding's worth of the next line showing through the // bottom of the strip — a sliced half-line of attribution, which is the one // thing that reads as broken rather than as lapped. const lines = Math.max(2, Math.floor((gauge - PAD_Y) / LINE_PX)); return PAD_Y + lines * LINE_PX; } const COURSES = COURSE_H.map((h) => { const gauge = (h - LAP - HEAD) / 2; return { h, gauge, exposure: exposureFor(gauge) }; }); const SLATE_W = 168; const COL_OFFSET = SLATE_W / 2; // half a slate — breaks the side lap const NAIL_Y = 18; // rotation origin, below the head const MIN_HIT = 44; // WCAG minimum, padded upward into transparent space only const SCALE_MIN = MIN_HIT / Math.min(...COURSES.map((c) => c.h)); // floor: smallest course never drops under 44px const SCALE_MAX = 1.6; const GUST_PERIOD = 4.8; // s — spec's 260px/s at the 1200px reference wall const GUST_WIDTH = 190; // px const AZIMUTH_PERIOD = 22.0; // s const AZIMUTH_DEG = 14; // reduced-motion freeze frame is spec'd at t=7.40s; the composed values below // (azimuth -6deg, one slate at max gust-lift, one fully read) are that frame // baked in directly rather than evaluated from the continuous functions, so // the still is exact and never depends on the (paused) clock. const LIFT_TARGET = -34; // deg const LIFT_K = 210; const LIFT_C = 19; const GUST_LIFT_K = 1200; const GUST_LIFT_C = 24; function isCentreNailed(index: number) { return index % 17 < 3; } // deterministic 0..1 hash, seeded by index — used for riven banding and gust // lift amplitude so both are byte-stable across renders without a stored RNG function hash(seed: number): number { let x = Math.sin(seed * 12.9898 + 78.233) * 43758.5453; x -= Math.floor(x); return x; } function springStep( value: number, velocity: number, target: number, k: number, c: number, dt: number ): [number, number] { const accel = -k * (value - target) - c * velocity; const nv = velocity + accel * dt; return [value + nv * dt, nv]; } // ---- token colour derivation (5 tokens only, HSL-lightness math) --------- function hexToRgb(hex: string): [number, number, number] { const m = /^#([0-9a-f]{3}|[0-9a-f]{6})$/i.exec(hex.trim()); if (!m) return [128, 128, 128]; let h = m[1]; if (h.length === 3) h = h.split("").map((c) => c + c).join(""); const n = parseInt(h, 16); return [(n >> 16) & 255, (n >> 8) & 255, n & 255]; } function rgbToHsl(r: number, g: number, b: number): [number, number, number] { r /= 255; g /= 255; b /= 255; const max = Math.max(r, g, b); const min = Math.min(r, g, b); let h = 0; let s = 0; const l = (max + min) / 2; const d = max - min; if (d !== 0) { s = l > 0.5 ? d / (2 - max - min) : d / (max + min); switch (max) { case r: h = (g - b) / d + (g < b ? 6 : 0); break; case g: h = (b - r) / d + 2; break; default: h = (r - g) / d + 4; } h /= 6; } return [h, s, l]; } function hslToRgb(h: number, s: number, l: number): [number, number, number] { if (s === 0) { const v = Math.round(l * 255); return [v, v, v]; } const q = l < 0.5 ? l * (1 + s) : l + s - l * s; const p = 2 * l - q; const hue2rgb = (t0: number) => { let t = t0; if (t < 0) t += 1; if (t > 1) t -= 1; if (t < 1 / 6) return p + (q - p) * 6 * t; if (t < 1 / 2) return q; if (t < 2 / 3) return p + (q - p) * (2 / 3 - t) * 6; return p; }; return [ Math.round(hue2rgb(h + 1 / 3) * 255), Math.round(hue2rgb(h) * 255), Math.round(hue2rgb(h - 1 / 3) * 255), ]; } function rgbToHex(r: number, g: number, b: number): string { const c = (n: number) => Math.max(0, Math.min(255, Math.round(n))).toString(16).padStart(2, "0"); return `#${c(r)}${c(g)}${c(b)}`; } /** Reuses a token's own hue/saturation but forces a target HSL lightness — * every derived colour below still traces back to a token read, never a * literal, but section 6's L values are what actually place it. */ function withLightness(hex: string, l: number): string { const [r, g, b] = hexToRgb(hex); const [h, s] = rgbToHsl(r, g, b); return rgbToHex(...hslToRgb(h, s, Math.max(0, Math.min(1, l)))); } function shiftLightness(hex: string, delta: number): string { const [r, g, b] = hexToRgb(hex); const [h, s, l] = rgbToHsl(r, g, b); return rgbToHex(...hslToRgb(h, s, Math.max(0, Math.min(1, l + delta)))); } function lightnessOf(hex: string): number { const [r, g, b] = hexToRgb(hex); return rgbToHsl(r, g, b)[2]; } interface Tokens { face: string; margin: string; shadow: string; edge: string; backing: string; riven: string; ink: string; inkMuted: string; } function readTokens(): Tokens { const cs = getComputedStyle(document.documentElement); const bg = cs.getPropertyValue("--background").trim() || "#ffffff"; const fg = cs.getPropertyValue("--foreground").trim() || "#171717"; const dark = lightnessOf(bg) < 0.5; // Section 6, retuned for card scale. The wall is a mid-value stone that // sits BELOW the page in dark and ABOVE the page in light — a dark stone // on a white page read as one undifferentiated slab, because every // internal step (margin, lap shadow, arris) had to fit under the face's // own lightness. Each theme therefore gets its own absolute lightness // ladder rather than a shared set of deltas. const L = dark ? { face: 0.44, margin: 0.53, shadow: 0.19, edge: 0.72, backing: 0.2, ink: 0.08, inkMuted: 0.22 } : { face: 0.66, margin: 0.76, shadow: 0.5, edge: 0.9, backing: 0.46, ink: 0.14, inkMuted: 0.32 }; const face = withLightness(fg, L.face); const margin = withLightness(fg, L.margin); // the lap shadow carries the whole image in a monochrome wall: measured at // -0.10L it was invisible at card scale and the courses read as one slab const shadow = withLightness(fg, L.shadow); const edge = withLightness(fg, L.edge); // the batten behind the wall: the half-slate stagger leaves a gap at the // start of every other course, and against the page background those gaps // read as missing tiles rather than as the wall carrying on behind const backing = withLightness(fg, L.backing); const riven = shiftLightness(face, 0.03); const ink = withLightness(fg, L.ink); const inkMuted = withLightness(fg, L.inkMuted); return { face, margin, shadow, edge, backing, riven, ink, inkMuted }; } // ---- default placeholder content ------------------------------------------ // Illustrative placeholder quotes: deliberately generic, attributed to a role // rather than to any person or company, so nothing here reads as a real // customer claim. Swap `items` for your own. const DEFAULT_QUOTES: { quote: string; name: string; role: string }[] = [ { quote: "We moved the whole team across in one afternoon.", name: "Engineering lead", role: "platform" }, { quote: "It replaced four tools we were stitching together.", name: "Product manager", role: "growth" }, { quote: "The defaults are sensible enough to ship on.", name: "Founder", role: "two-person studio" }, { quote: "Onboarding takes a morning, not a fortnight.", name: "Head of design", role: "in-house team" }, { quote: "Nobody argues about which copy is current now.", name: "Operations lead", role: "support" }, { quote: "Tickets about the old export flow stopped.", name: "Customer success", role: "EMEA" }, { quote: "It fits how we already work, not the reverse.", name: "Staff engineer", role: "infrastructure" }, { quote: "The audit trail answered a question we dreaded.", name: "Security lead", role: "compliance" }, { quote: "Rolling a mistake back is a single click.", name: "Tech lead", role: "web" }, { quote: "Design and engineering read the same source.", name: "Design engineer", role: "design systems" }, { quote: "We stopped keeping a spreadsheet nobody trusted.", name: "Analytics lead", role: "data" }, { quote: "Quiet, fast, and it has never lost our work.", name: "Principal engineer", role: "core services" }, { quote: "The migration was the boring part of the quarter.", name: "Delivery manager", role: "programmes" }, { quote: "It is the first internal tool people ask for.", name: "Chief of staff", role: "operations" }, { quote: "Two years in, we have not outgrown it.", name: "Director of engineering", role: "product" }, { quote: "Handover notes write themselves now.", name: "Programme lead", role: "delivery" }, { quote: "Nothing about it has surprised us badly.", name: "Platform architect", role: "reliability" }, { quote: "The people who resisted it use it most.", name: "Team lead", role: "customer platform" }, ]; const DEFAULT_ITEMS: SlateTestimonial[] = DEFAULT_QUOTES.map((q, i) => ({ id: `slate-${i + 1}`, ...q, })); interface Slate { index: number; row: number; col: number; x: number; // design px, unscaled top: number; // design px, unscaled — top of this course's exposed gauge h: number; gauge: number; exposure: number; centreNailed: boolean; } function layout(items: SlateTestimonial[], columns: number): { slates: Slate[]; naturalW: number; naturalH: number } { const cols = Math.max(1, columns); const rows = Math.ceil(items.length / cols); const courseTop: number[] = [0]; for (let r = 0; r < rows; r++) courseTop.push(courseTop[r] + COURSES[r % COURSES.length].exposure); const slates: Slate[] = items.map((_, i) => { const row = Math.floor(i / cols); const col = i % cols; const course = COURSES[row % COURSES.length]; const offset = row % 2 === 1 ? COL_OFFSET : 0; return { index: i, row, col, x: col * SLATE_W + offset, top: courseTop[row], h: course.h, gauge: course.gauge, exposure: course.exposure, centreNailed: isCentreNailed(i), }; }); const naturalW = cols * SLATE_W + COL_OFFSET; const naturalH = courseTop[rows]; // sum of every course's exposure — the last course's excess is trimmed return { slates, naturalW, naturalH }; } export function SlateGauge({ items = DEFAULT_ITEMS, columns = 3, heading = "What teams say", className = "", }: SlateGaugeProps) { const hostRef = useRef(null); const wallRef = useRef(null); const slateFaceRefs = useRef>({}); const rivenRefs = useRef>({}); const [liftedIndex, setLiftedIndex] = useState(null); const [scale, setScale] = useState(1); const liftedRef = useRef(null); liftedRef.current = liftedIndex; const { slates, naturalW, naturalH } = useMemo(() => layout(items, columns), [items, columns]); // reduced-motion picks one representative slate to hold lifted and one // centre-nailed slate near the frozen gust to hold mid-clatter, so the // single composed frame shows every state the wall has at once (spec §5) const staticPicks = useMemo(() => { const gustCol = Math.min(1, Math.max(0, columns - 1)); const lifted = Math.min(2, slates.length - 1); const near = slates.find((s) => s.centreNailed && s.col === gustCol) ?? slates.find((s) => s.centreNailed); return { lifted, microLift: near?.index ?? null }; }, [slates, columns]); const rivenBg = useMemo(() => { // deterministic per-slate band pattern (spacing only — colours are // re-applied on token read) computed once so it is byte-stable forever const maps: Record = {}; for (const s of slates) { const bands: { start: number; end: number }[] = []; let y = 0; let seed = s.index * 97 + 11; while (y < s.h) { const w = 3 + hash(seed) * 6; // 3-9px bands.push({ start: y, end: Math.min(s.h, y + w) }); y += w; seed += 1; } maps[s.index] = bands; } return maps; }, [slates]); // ---- token read, geometry fit, and the whole idle loop ----------------- useLayoutEffect(() => { const host = hostRef.current; const wall = wallRef.current; if (!host || !wall) return; // token read happens before anything paints — see the class comment let tokens = readTokens(); const applyTokens = () => { wall.style.setProperty("--slate-face", tokens.face); wall.style.setProperty("--slate-margin", tokens.margin); wall.style.setProperty("--slate-shadow-color", tokens.shadow); wall.style.setProperty("--slate-edge", tokens.edge); wall.style.setProperty("--slate-backing", tokens.backing); wall.style.setProperty("--slate-riven", tokens.riven); wall.style.setProperty("--slate-ink", tokens.ink); wall.style.setProperty("--slate-ink-muted", tokens.inkMuted); // repaint riven band gradients with the fresh colour pair — percentage // stops (of the slate's own full height) so the pattern never needs to // be re-scaled when the fit scale or the lift height changes for (const s of slates) { const el = rivenRefs.current[s.index]; if (!el) continue; const stops = rivenBg[s.index] .map((b, i) => { // ±0.03L fracture banding (section 6) — a texture on the stone // itself, distinct from the sky-lit margin tint layered above it const c = i % 2 === 0 ? tokens.face : tokens.riven; return `${c} ${(b.start / s.h) * 100}%, ${c} ${(b.end / s.h) * 100}%`; }) .join(", "); el.style.backgroundImage = `linear-gradient(to bottom, ${stops})`; } }; applyTokens(); const reduced = window.matchMedia("(prefers-reduced-motion: reduce)").matches; const fit = () => { const rect = host.getBoundingClientRect(); if (rect.width < 4 || rect.height < 4) return; const s = Math.max(SCALE_MIN, Math.min(SCALE_MAX, Math.min(rect.width / naturalW, rect.height / naturalH))); setScale(s); }; fit(); const ro = new ResizeObserver(fit); ro.observe(host); if (reduced) { // one composed still frame, byte-stable: no loop, no listeners wall.style.setProperty("--wall-azimuth", "-6"); if (staticPicks.microLift != null) { const el = slateFaceRefs.current[staticPicks.microLift]; if (el) el.style.setProperty("--gust-lift", "5"); } setLiftedIndex(staticPicks.lifted); const liftedEl = slateFaceRefs.current[staticPicks.lifted]; if (liftedEl) liftedEl.style.transform = `rotate(${LIFT_TARGET}deg)`; return () => ro.disconnect(); } // ---- continuous idle loop: gust field + light azimuth + micro-lifts -- let raf = 0; let running = false; let last = performance.now(); let t = 0; const liftState = new Map(); let readLift = { v: 0, vel: 0 }; // the slate currently returning after release is tracked separately from // the one actively held, since liftedIndex can flip to null the instant // a pointer leaves — the spring still needs a face to write to let lastHeld: number | null = null; const tick = (now: number) => { raf = requestAnimationFrame(tick); const dt = Math.min(0.05, Math.max(0, (now - last) / 1000)); last = now; t += dt; const azimuth = AZIMUTH_DEG * Math.cos((2 * Math.PI * t) / AZIMUTH_PERIOD); wall.style.setProperty("--wall-azimuth", azimuth.toFixed(2)); // gust math stays entirely in natural (unscaled) design units, the same // space slate.x already lives in — the fit `scale` only ever touches // the JSX render, never this comparison const span = naturalW + GUST_WIDTH * 2; const frac = (t % GUST_PERIOD) / GUST_PERIOD; const gustX = -GUST_WIDTH + frac * span; for (const s of slates) { if (!s.centreNailed) continue; const el = slateFaceRefs.current[s.index]; if (!el) continue; const centerX = s.x + SLATE_W / 2; const inGust = Math.abs(centerX - gustX) < GUST_WIDTH / 2; const amp = 2.5 + hash(s.index * 31 + 7) * 2.5; let st = liftState.get(s.index); if (!st) { st = { v: 0, vel: 0, target: 0 }; liftState.set(s.index, st); } st.target = inGust ? amp : 0; const [nv, nvel] = springStep(st.v, st.vel, st.target, GUST_LIFT_K, GUST_LIFT_C, dt); st.v = nv; st.vel = nvel; el.style.setProperty("--gust-lift", st.v.toFixed(2)); } const held = liftedRef.current; const activeIndex = held ?? lastHeld; if (held != null) lastHeld = held; if (activeIndex != null) { const el = slateFaceRefs.current[activeIndex]; const target = held != null ? LIFT_TARGET : 0; const [nv, nvel] = springStep(readLift.v, readLift.vel, target, LIFT_K, LIFT_C, dt); readLift = { v: nv, vel: nvel }; if (el) el.style.transform = nv === 0 ? "" : `rotate(${nv.toFixed(2)}deg)`; if (held == null && Math.abs(nv) < 0.02 && Math.abs(nvel) < 0.02) { if (el) el.style.transform = ""; lastHeld = null; readLift = { v: 0, vel: 0 }; } } }; running = true; raf = requestAnimationFrame(tick); const io = new IntersectionObserver( (entries) => { const visible = entries.some((e) => e.isIntersecting); if (visible && !running) { running = true; last = performance.now(); raf = requestAnimationFrame(tick); } else if (!visible && running) { running = false; cancelAnimationFrame(raf); } }, { threshold: 0 } ); io.observe(host); const onVis = () => { if (document.hidden && running) { running = false; cancelAnimationFrame(raf); } else if (!document.hidden && !running) { running = true; last = performance.now(); raf = requestAnimationFrame(tick); } }; document.addEventListener("visibilitychange", onVis); const mo = new MutationObserver(() => { tokens = readTokens(); applyTokens(); }); mo.observe(document.documentElement, { attributes: true, attributeFilter: ["class"] }); return () => { ro.disconnect(); io.disconnect(); document.removeEventListener("visibilitychange", onVis); mo.disconnect(); cancelAnimationFrame(raf); }; // eslint-disable-next-line react-hooks/exhaustive-deps }, [slates, naturalW, naturalH, rivenBg, staticPicks]); const toggle = (index: number) => { setLiftedIndex((prev) => (prev === index ? null : index)); }; return (

{heading}

{/* The eaves. Every interior course is cut off by the slate lapping over it, which is what reads as overlap; the bottom course has nothing above it, so without a rail its cut edge reads as truncated text instead of as the foot of the wall. */}