Tracking
React + Tailwind
import { useState } from 'react';
const WORD = 'MOTION';
const css = `
.slider-tracking { display: grid; justify-items: center; gap: 14px; width: 230px; }
.slider-tracking__word { display: flex; justify-content: center; height: 40px; color: light-dark(#373a40, #f1f2f3); font-size: 28px; font-weight: 600; line-height: 40px; }
.slider-tracking__char { display: inline-block; margin-right: calc((var(--slider-tracking-v) * 0.55 - 0.05) * 1em); transition: margin-right 0.45s cubic-bezier(0.3, 1.4, 0.5, 1); transition-delay: calc(var(--i) * 35ms); }
.slider-tracking__char:last-child { margin-right: 0; }
.slider-tracking__val { color: light-dark(#5f626a, #a7abb2); font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: 11px; font-variant-numeric: tabular-nums; }
.slider-tracking__track { position: relative; width: 100%; height: 24px; }
.slider-tracking__rail { position: absolute; left: 0; right: 0; top: 11px; height: 2px; background: light-dark(#dbdde1, #2e3035); }
.slider-tracking__rail::before, .slider-tracking__rail::after { content: ''; position: absolute; top: -4px; width: 2px; height: 10px; background: light-dark(#6d7179, #7d8087); }
.slider-tracking__rail::before { left: 0; }
.slider-tracking__rail::after { right: 0; }
.slider-tracking__thumb { position: absolute; top: 2px; left: calc(var(--slider-tracking-v) * (100% - 24px)); width: 24px; height: 20px; border-radius: 5px; background: light-dark(#373a40, #f1f2f3); box-shadow: 0 2px 6px light-dark(rgba(0, 0, 0, 0.12), rgba(0, 0, 0, 0.4)); }
.slider-tracking__thumb::before, .slider-tracking__thumb::after { content: ''; position: absolute; top: 6px; border: 4px solid transparent; }
.slider-tracking__thumb::before { left: 1px; border-right-color: light-dark(#dbdde1, #2e3035); }
.slider-tracking__thumb::after { right: 1px; border-left-color: light-dark(#dbdde1, #2e3035); }
.slider-tracking:has(.slider-tracking__input:focus-visible) .slider-tracking__thumb { outline: 2px solid light-dark(#50535b, #c6c8cd); outline-offset: 3px; }
.slider-tracking__input { position: absolute; inset: 0; width: 100%; height: 100%; margin: 0; opacity: 0; cursor: pointer; -webkit-appearance: none; appearance: none; background: none; }
.slider-tracking__input::-webkit-slider-thumb { -webkit-appearance: none; width: 24px; height: 20px; }
.slider-tracking__input::-moz-range-thumb { width: 24px; height: 20px; border: 0; }
@media (prefers-reduced-motion: reduce) {
.slider-tracking__char { transition: none; }
}
`;
export function TrackingSlider() {
const [v, setV] = useState(30);
const em = ((v / 100) * 0.55 - 0.05).toFixed(2);
return (
<>
<style>
{css}
</style>
<div className="slider-tracking" style={{ '--slider-tracking-v': v / 100 } as React.CSSProperties}>
<span className="slider-tracking__word" aria-hidden="true">
{WORD.split('').map((c, i) => (
<span key={i} className="slider-tracking__char" style={{ '--i': i } as React.CSSProperties}>
{c}
</span>
))}
</span>
<span className="slider-tracking__val" aria-hidden="true">
{em} em
</span>
<div className="slider-tracking__track">
<span className="slider-tracking__rail" />
<span className="slider-tracking__thumb" />
<input className="slider-tracking__input" type="range" min={0} max={100} value={v} onChange={(e) => setV(+e.target.value)} aria-label="Letter spacing" aria-valuetext={`${em} em`} />
</div>
</div>
</>
);
}Markup where the component goes, CSS in your stylesheet, script before </body>. In Vue, Svelte or Angular, call initSliderTracking(el) on the mounted element instead.
HTML
<div class="slider-tracking" style="--slider-tracking-v:0.3">
<span class="slider-tracking__word" aria-hidden="true">
<span class="slider-tracking__char" style="--i:0">M</span>
<span class="slider-tracking__char" style="--i:1">O</span>
<span class="slider-tracking__char" style="--i:2">T</span>
<span class="slider-tracking__char" style="--i:3">I</span>
<span class="slider-tracking__char" style="--i:4">O</span>
<span class="slider-tracking__char" style="--i:5">N</span>
</span>
<span class="slider-tracking__val" aria-hidden="true">0.12 em</span>
<div class="slider-tracking__track">
<span class="slider-tracking__rail"></span>
<span class="slider-tracking__thumb"></span>
<input class="slider-tracking__input" type="range" min="0" max="100" aria-label="Letter spacing" aria-valuetext="0.12 em" value="30"/>
</div>
</div>CSS
.slider-tracking { display: grid; justify-items: center; gap: 14px; width: 230px; }
.slider-tracking__word { display: flex; justify-content: center; height: 40px; color: light-dark(#373a40, #f1f2f3); font-size: 28px; font-weight: 600; line-height: 40px; }
.slider-tracking__char { display: inline-block; margin-right: calc((var(--slider-tracking-v) * 0.55 - 0.05) * 1em); transition: margin-right 0.45s cubic-bezier(0.3, 1.4, 0.5, 1); transition-delay: calc(var(--i) * 35ms); }
.slider-tracking__char:last-child { margin-right: 0; }
.slider-tracking__val { color: light-dark(#5f626a, #a7abb2); font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: 11px; font-variant-numeric: tabular-nums; }
.slider-tracking__track { position: relative; width: 100%; height: 24px; }
.slider-tracking__rail { position: absolute; left: 0; right: 0; top: 11px; height: 2px; background: light-dark(#dbdde1, #2e3035); }
.slider-tracking__rail::before, .slider-tracking__rail::after { content: ''; position: absolute; top: -4px; width: 2px; height: 10px; background: light-dark(#6d7179, #7d8087); }
.slider-tracking__rail::before { left: 0; }
.slider-tracking__rail::after { right: 0; }
.slider-tracking__thumb { position: absolute; top: 2px; left: calc(var(--slider-tracking-v) * (100% - 24px)); width: 24px; height: 20px; border-radius: 5px; background: light-dark(#373a40, #f1f2f3); box-shadow: 0 2px 6px light-dark(rgba(0, 0, 0, 0.12), rgba(0, 0, 0, 0.4)); }
.slider-tracking__thumb::before, .slider-tracking__thumb::after { content: ''; position: absolute; top: 6px; border: 4px solid transparent; }
.slider-tracking__thumb::before { left: 1px; border-right-color: light-dark(#dbdde1, #2e3035); }
.slider-tracking__thumb::after { right: 1px; border-left-color: light-dark(#dbdde1, #2e3035); }
.slider-tracking:has(.slider-tracking__input:focus-visible) .slider-tracking__thumb { outline: 2px solid light-dark(#50535b, #c6c8cd); outline-offset: 3px; }
.slider-tracking__input { position: absolute; inset: 0; width: 100%; height: 100%; margin: 0; opacity: 0; cursor: pointer; -webkit-appearance: none; appearance: none; background: none; }
.slider-tracking__input::-webkit-slider-thumb { -webkit-appearance: none; width: 24px; height: 20px; }
.slider-tracking__input::-moz-range-thumb { width: 24px; height: 20px; border: 0; }
@media (prefers-reduced-motion: reduce) {
.slider-tracking__char { transition: none; }
}JavaScript
function initSliderTracking(root) {
var input = root.querySelector('.slider-tracking__input');
var read = root.querySelector('.slider-tracking__val');
function update() {
var v = +input.value;
var em = ((v / 100) * 0.55 - 0.05).toFixed(2);
root.style.setProperty('--slider-tracking-v', v / 100);
read.textContent = em + ' em';
input.setAttribute('aria-valuetext', em + ' em');
}
input.addEventListener('input', update);
update();
return function () { input.removeEventListener('input', update); };
}
document.querySelectorAll('.slider-tracking').forEach(initSliderTracking);Goal: Create a "Tracking" slider.
Visual behavior: A letter-spacing slider: the letters of the word spread apart and draw together as you drag, each a beat after the one before, with the value in em below.
Technique:
- A real <input type="range"> lies over the drawing, transparent (opacity 0, appearance none), with its thumb hit area sized to the drawn thumb, so dragging, clicking the track and the arrow, Page Up/Down, Home and End keys all work natively. The drawing is aria-hidden.
- The value is written to one CSS custom property (0 to 1) on the root; each letter's right margin is calc() of it in em, and each carries its index as a transition delay, so the spacing ripples along the word. The word is centred, so it grows from the middle.
- :has(input:focus-visible) outlines the drawn thumb, so keyboard focus is visible though the input itself is not.
Accessibility: A native range input with an aria-label and an aria-valuetext in words, so a screen reader announces the reading rather than a bare number; keyboard focus outlines the drawn thumb. Under prefers-reduced-motion the letters move without easing.
My stack: {{USER_STACK}}
My styling: {{USER_STYLING}}
My constraints: {{USER_CONSTRAINTS}}
My colors: neutral only. Black, white and grays, no hues. Use the color values above as written, or my project's closest neutral tokens.
Return a single self-contained component. No dependencies.Goal: Create a "Tracking" slider.
Visual behavior: A letter-spacing slider: the letters of the word spread apart and draw together as you drag, each a beat after the one before, with the value in em below.
Technique:
- A real <input type="range"> lies over the drawing, transparent (opacity 0, appearance none), with its thumb hit area sized to the drawn thumb, so dragging, clicking the track and the arrow, Page Up/Down, Home and End keys all work natively. The drawing is aria-hidden.
- The value is written to one CSS custom property (0 to 1) on the root; each letter's right margin is calc() of it in em, and each carries its index as a transition delay, so the spacing ripples along the word. The word is centred, so it grows from the middle.
- :has(input:focus-visible) outlines the drawn thumb, so keyboard focus is visible though the input itself is not.
Accessibility: A native range input with an aria-label and an aria-valuetext in words, so a screen reader announces the reading rather than a bare number; keyboard focus outlines the drawn thumb. Under prefers-reduced-motion the letters move without easing.
My stack: {{USER_STACK}}
My styling: {{USER_STYLING}}
My constraints: {{USER_CONSTRAINTS}}
My colors: use my project's existing color tokens. The color values above are grayscale placeholders. Map each one by its role (surface, text, border, accent, glow) to my theme, and keep their relative lightness so contrast and the effect still read.
Return a single self-contained component. No dependencies.Paste into Claude, ChatGPT or Cursor after filling in {{USER_STACK}}, {{USER_STYLING}} and {{USER_CONSTRAINTS}}. Neutral keeps the greys you see here; Match my project asks the model to map them onto your own colour tokens.
Free to use in any project, commercial included. MIT-0, no attribution required. Licence
About this component
A letter-spacing slider: the letters of the word spread apart and draw together as you drag, each a beat after the one before, with the value in em below.
- Dependencies
- None
- Difficulty
- Beginner
- Triggers
- state change, delay stagger
- Techniques
- css variables, css transition
- Reduced motion
- Respected
- Theme
- Light and dark (follows your page's color-scheme)
A native range input with an aria-label and an aria-valuetext in words, so a screen reader announces the reading rather than a bare number; keyboard focus outlines the drawn thumb. Under prefers-reduced-motion the letters move without easing.