A still — with scripts on, it runs right here The demo itself — scroll inside the frame
A still — with scripts on, it runs right here The demo itself — scroll inside the frame
Copy and paste, or save a file and hand it over. For a machine with no network, one “Everything” file is enough.
Everything in this panel, including the contents behind each URL, in one Markdown file — Large, so it goes as a file (copy is for 32 KB and under)
Letter-spacing on scroll — Letter-spacing on scroll Build three large headings whose letter-spacing opens and closes with scroll. Take each heading section's progress through the viewport as --p (0–1), and stretch the 0.25–0.75 part of it — from fully entered to starting to leave — to 0–1. `letter-spacing` starts at -0.04em, peaks at 0.3em when the section reaches the middle of the viewport, and returns to 0 as it leaves. Tie the value to scroll position, not time; do not add a `transition`. Set the headings bold at `clamp(28px, 7vw, 96px)`, eight characters or fewer, so they stay on one line at the widest spacing (0.3em) and no horizontal scrollbar appears. Fix each heading's box at two lines tall (font size × 2.6) so nothing below it moves. With reduced motion, hold the letter-spacing at 0. Implement with CSS `calc()`, `min()` and `max()` plus plain JavaScript that writes scroll progress to a CSS variable; do not use a library. Do not drop: - Spacing runs -0.04em → 0.3em → 0, peaking when the section is centred in the viewport - At the widest spacing the heading still fits on one line (from 340px wide up) and never causes horizontal scroll - The heading box has a fixed height, so the page height never changes while scrolling - With reduced motion, spacing stays at 0 A working example (one self-contained HTML file): https://design-vault.pages.dev/designs/motion-tracking-expand/demo.html
/designs/motion-tracking-expand/demo.html — One self-contained HTML file. CSS and plain JavaScript only; it fetches nothing.
<!doctype html>
<html lang="ja">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>26 字間の開閉 — Letter-spacing on scroll</title>
<style>
/* dv-motion-base:start */
:root {
--ground: #FFFFFF;
--surface: #F3F5F8;
--ink: #14181F;
--muted: #5A6472;
--accent: #1F5FA8;
--rule: #D8DDE4;
--accent-soft: color-mix(in srgb, var(--accent) 12%, var(--ground));
--accent-mid: color-mix(in srgb, var(--accent) 45%, var(--ground));
--shade: color-mix(in srgb, var(--ink) 14%, transparent);
--font: "Zen Kaku Gothic New", "Hiragino Sans", "Noto Sans JP", "Yu Gothic", system-ui, sans-serif;
--mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
--t-label: 13px;
--t-body: 16px;
--t-lead: 20px;
--t-h2: 32px;
--t-h1: clamp(40px, 7vw, 72px);
--s1: 4px;
--s2: 8px;
--s3: 16px;
--s4: 24px;
--s5: 40px;
--s6: 64px;
--s7: 104px;
--radius: 12px;
--ease: cubic-bezier(.2, .7, .2, 1);
--dur: .7s;
--measure: 1080px;
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
margin: 0;
background: var(--ground);
color: var(--ink);
font-family: var(--font);
font-size: var(--t-body);
line-height: 1.7;
font-feature-settings: "palt";
overflow-x: hidden;
}
h1, h2, h3, p, ul, ol, figure { margin: 0; padding: 0; }
ul, ol { list-style: none; }
.dv-wrap { width: min(100% - 2 * var(--s4), var(--measure)); margin-inline: auto; }
.dv-label {
min-height: 72vh;
display: grid;
align-content: center;
gap: var(--s3);
padding-block: var(--s6);
border-bottom: 1px solid var(--rule);
}
.dv-num { font-family: var(--mono); font-size: var(--t-lead); font-weight: 700; color: var(--accent); letter-spacing: .04em; }
.dv-name { font-size: var(--t-h1); font-weight: 700; line-height: 1.15; letter-spacing: .01em; }
.dv-ai { font-family: var(--mono); font-size: var(--t-lead); color: var(--muted); }
.dv-desc { font-size: var(--t-lead); color: var(--ink); }
.dv-hint { font-size: var(--t-label); color: var(--muted); letter-spacing: .12em; margin-top: var(--s4); }
.dv-stage { padding-block: var(--s7); }
.dv-h2 { font-size: var(--t-h2); font-weight: 700; line-height: 1.3; }
.dv-lead { font-size: var(--t-lead); color: var(--muted); }
.dv-eyebrow { font-family: var(--mono); font-size: var(--t-label); color: var(--accent); letter-spacing: .12em; text-transform: uppercase; }
.dv-card { background: var(--surface); border: 1px solid var(--rule); border-radius: var(--radius); padding: var(--s4); }
.dv-ph {
border-radius: var(--radius);
background: linear-gradient(135deg, var(--accent-soft), var(--accent-mid) 60%, var(--accent));
aspect-ratio: 16 / 9;
}
.dv-ph--alt { background: linear-gradient(200deg, var(--surface), var(--accent-soft) 55%, var(--accent-mid)); }
.dv-ph--ink { background: linear-gradient(160deg, var(--ink), color-mix(in srgb, var(--ink) 55%, var(--accent))); }
.dv-end {
min-height: 60vh;
display: grid;
place-items: center;
border-top: 1px solid var(--rule);
color: var(--muted);
font-family: var(--mono);
font-size: var(--t-label);
letter-spacing: .12em;
}
/* dv-motion-base:end */
/* ---- この演出だけの CSS。色は var(--…) か color-mix() のみ ---- */
.trk-list { display: grid; gap: 36vh; padding-block: 24vh; }
.trk {
--fs: clamp(28px, 7vw, 96px);
/* 画面に入りきってから出始めるまで（--p が 0.25〜0.75）を 0〜1 に引き伸ばす */
--q: clamp(0, (var(--p, 1) - 0.25) / 0.5, 1);
display: grid;
gap: var(--s3);
padding-block: var(--s4);
border-block: 1px solid var(--rule);
}
/* 箱の高さは 2 行ぶんで固定する。字は 7vw 以下なので、字間が最大でも 8 字は 1 行に収まり、下の要素が動かず --p が揺れない */
.trk-box { height: calc(var(--fs) * 2.6); display: grid; align-content: center; }
.trk-head {
font-size: var(--fs);
font-weight: 700;
line-height: 1.3;
overflow-wrap: anywhere;
/* -0.04em（--q = 0）→ 0.3em（0.5）→ 0（1） */
letter-spacing: calc((-0.04 + 0.68 * min(var(--q), 0.5) - 0.6 * max(var(--q) - 0.5, 0)) * 1em);
}
.trk-read { font-family: var(--mono); font-size: var(--t-label); color: var(--muted); letter-spacing: .04em; font-variant-numeric: tabular-nums; }
@media (prefers-reduced-motion: reduce) {
.trk-head { letter-spacing: 0; }
}
</style>
</head>
<body data-motion-number="26">
<header class="dv-label">
<div class="dv-wrap">
<p class="dv-num">26</p>
<h1 class="dv-name">字間の開閉</h1>
<p class="dv-ai">Letter-spacing on scroll</p>
<p class="dv-desc">字間がスクロールで広がり、また詰まる</p>
<p class="dv-hint">SCROLL ↓</p>
</div>
</header>
<main class="dv-stage">
<div class="dv-wrap">
<section class="dv-card">
<p class="dv-eyebrow">Section 1</p>
<h2 class="dv-h2">見出しが入ります</h2>
<p class="dv-lead">本文のダミーです。このあとの大見出しは、画面の中央へ近づくほど字間が広がります。</p>
</section>
<div class="trk-list">
<section class="trk" data-progress="through">
<p class="dv-eyebrow">Heading 1</p>
<div class="trk-box"><h2 class="trk-head">見出しが入ります</h2></div>
<p class="trk-read">letter-spacing: <span data-read>0.00</span>em</p>
</section>
<section class="trk" data-progress="through">
<p class="dv-eyebrow">Heading 2</p>
<div class="trk-box"><h2 class="trk-head">字間がひらきます</h2></div>
<p class="trk-read">letter-spacing: <span data-read>0.00</span>em</p>
</section>
<section class="trk" data-progress="through">
<p class="dv-eyebrow">Heading 3</p>
<div class="trk-box"><h2 class="trk-head">もとに戻ります</h2></div>
<p class="trk-read">letter-spacing: <span data-read>0.00</span>em</p>
</section>
</div>
<section class="dv-card">
<p class="dv-eyebrow">Section 2</p>
<h2 class="dv-h2">見出しが入ります</h2>
<p class="dv-lead">本文のダミーです。中央を過ぎた見出しは、字間が詰まって通常の組みに戻ります。</p>
</section>
</div>
</main>
<footer class="dv-end">END — 26 字間の開閉</footer>
<script>
/* dv-motion-helpers:start */
const dvReduce = matchMedia('(prefers-reduced-motion: reduce)').matches;
document.documentElement.classList.add('js');
/**
* 画面に入った要素へ .is-in を付ける。
* data-reveal="repeat" の要素は画面を出たら外す（何度でも再生）。
*/
function dvReveal(selector = '[data-reveal]', { threshold = 0.2, rootMargin = '0px 0px -8% 0px' } = {}) {
const els = [...document.querySelectorAll(selector)];
if (dvReduce || !('IntersectionObserver' in window)) {
els.forEach((el) => el.classList.add('is-in'));
return;
}
const io = new IntersectionObserver((entries) => {
for (const e of entries) {
if (e.isIntersecting) {
e.target.classList.add('is-in');
if (e.target.dataset.reveal !== 'repeat') io.unobserve(e.target);
} else if (e.target.dataset.reveal === 'repeat') {
e.target.classList.remove('is-in');
}
}
}, { threshold, rootMargin });
els.forEach((el) => io.observe(el));
}
/**
* スクロール量を 0〜1 にして、各 [data-progress] 要素の CSS 変数 --p に書く。
* data-progress="through" : 要素の上端が画面の下端に来たとき 0、下端が画面の上端を抜けたとき 1
* data-progress="pin" : 要素の上端が画面の上端に来たとき 0、下端が画面の下端に来たとき 1
* （中に position: sticky の箱を持つ、背の高い区画用）
* data-progress="page" : ページ全体のスクロール量
* onUpdate(el, p) を渡すと、値が変わるたびに呼ばれる。
*/
function dvProgress(onUpdate) {
const els = [...document.querySelectorAll('[data-progress]')];
const clamp = (n) => Math.min(1, Math.max(0, n));
let queued = false;
const measure = () => {
queued = false;
const vh = window.innerHeight;
for (const el of els) {
const r = el.getBoundingClientRect();
let p;
if (el.dataset.progress === 'pin') p = r.height > vh ? -r.top / (r.height - vh) : 0;
else if (el.dataset.progress === 'page') {
const max = document.documentElement.scrollHeight - vh;
p = max > 0 ? window.scrollY / max : 0;
} else p = (vh - r.top) / (vh + r.height);
p = clamp(p);
el.style.setProperty('--p', p.toFixed(4));
if (onUpdate) onUpdate(el, p);
}
};
const request = () => {
if (!queued) { queued = true; requestAnimationFrame(measure); }
};
addEventListener('scroll', request, { passive: true });
addEventListener('resize', request);
measure();
}
/* dv-motion-helpers:end */
/* ---- この演出だけの JS ---- */
// 字間の値は CSS が --p から作る。ここでは、その結果を読んで数値の表示へ写すだけ。
if (!dvReduce) {
dvProgress((el) => {
const cs = getComputedStyle(el.querySelector('.trk-head'));
const em = parseFloat(cs.letterSpacing) / parseFloat(cs.fontSize);
el.querySelector('[data-read]').textContent = (Number.isFinite(em) ? em : 0).toFixed(2);
});
}
</script>
</body>
</html>