Curve Lab — Bézier playground

<!-- Original layout, SVG/CSS artwork and JavaScript © 2026 XXC Templates. MIT License.
Illustrative sample content and data; no real accounts, purchases or bookings. -->
<main>
  <header class="intro">
    <div>
      <div class="kicker">CURVE LAB / GEOMETRY IN MOTION</div>
      <h1>A curve has character.</h1>
      <p>Shape a cubic Bézier by changing its two control points.</p>
    </div>
  </header>
  <section class="panel">
    <svg
      id="chart"
      viewBox="0 0 700 270"
      role="img"
      aria-label="Interactive cubic Bézier curve"
    ></svg>
    <div class="curve-controls">
      <label
        >X1 <input data-control="x1" type="range" min="0" max="700" value="160" /><output
          id="out-x1"
          >160</output
        ></label
      ><label
        >Y1 <input data-control="y1" type="range" min="0" max="270" value="30" /><output id="out-y1"
          >30</output
        ></label
      ><label
        >X2 <input data-control="x2" type="range" min="0" max="700" value="520" /><output
          id="out-x2"
          >520</output
        ></label
      ><label
        >Y2 <input data-control="y2" type="range" min="0" max="270" value="230" /><output
          id="out-y2"
          >230</output
        ></label
      >
    </div>
    <div class="toolbar">
      <button id="change">Try another curve</button><button id="reset">Reset</button>
    </div>
    <code id="path-code"></code><output id="status" class="status" aria-live="polite"></output>
  </section>
</main>

:root {
  --bg: #0b1222;
  --panel: #121e33;
  --text: #e9f1ff;
  --muted: #9aaeca;
  --line: #253852;
  --accent: #82b6ff;
}
/* Original XXC Templates Studio collection. MIT; sample data only. */
* {
  box-sizing: border-box;
}
html {
  color-scheme: dark;
}
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font:
    14px/1.6 system-ui,
    -apple-system,
    BlinkMacSystemFont,
    "Segoe UI",
    sans-serif;
  padding: clamp(18px, 4vw, 40px);
  min-height: 100vh;
}
h1,
h2,
h3,
p {
  margin: 0;
}
h1 {
  font-size: clamp(27px, 4.8vw, 46px);
  line-height: 1.07;
  letter-spacing: -0.055em;
  font-weight: 650;
}
h2 {
  font-size: 22px;
  letter-spacing: -0.025em;
  line-height: 1.2;
}
h3 {
  font-size: 15px;
}
p {
  color: var(--muted);
}
button,
input,
select {
  font: inherit;
}
button,
a,
input,
select,
summary {
  touch-action: manipulation;
}
button {
  cursor: pointer;
  color: var(--text);
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 9px;
  padding: 9px 14px;
  font-size: 12px;
}
button:hover {
  border-color: var(--accent);
}
button[aria-pressed="true"],
button.active {
  background: var(--accent);
  color: var(--bg);
  border-color: var(--accent);
}
button:disabled {
  opacity: 0.5;
  cursor: default;
}
button:focus-visible,
a:focus-visible,
input:focus-visible,
select:focus-visible,
summary:focus-visible,
[tabindex]:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 4px;
}
a {
  color: inherit;
  text-underline-offset: 4px;
}
input,
select {
  min-width: 0;
  max-width: 100%;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 9px;
}
input[type="range"] {
  accent-color: var(--accent);
  padding: 0;
}
input[type="checkbox"] {
  accent-color: var(--accent);
}
label {
  display: flex;
  gap: 8px;
  align-items: center;
  font-size: 12px;
  color: var(--muted);
}
svg {
  max-width: 100%;
  display: block;
}
img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
main {
  max-width: 1120px;
  margin: auto;
  min-width: 0;
}
.kicker {
  text-transform: uppercase;
  letter-spacing: 0.17em;
  font:
    10px/1.6 ui-monospace,
    monospace;
  color: var(--accent);
}
.intro {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  align-items: center;
  margin-bottom: 25px;
}
.intro h1 {
  margin: 8px 0 10px;
}
.intro p {
  max-width: 470px;
  font-size: 13px;
}
.badge {
  display: inline-flex;
  border: 1px solid var(--line);
  border-radius: 50px;
  padding: 5px 10px;
  font:
    10px ui-monospace,
    monospace;
  color: var(--muted);
}
.panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 22px;
  min-width: 0;
}
.toolbar {
  display: flex;
  gap: 9px;
  flex-wrap: wrap;
  align-items: center;
  margin: 16px 0;
}
.primary {
  background: var(--accent);
  color: var(--bg);
  border-color: var(--accent);
}
.grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 15px;
}
.muted {
  color: var(--muted);
}
.metric {
  font-size: 36px;
  letter-spacing: -0.05em;
  font-weight: 600;
}
.mono {
  font-family: ui-monospace, monospace;
}
.rule {
  border: 0;
  border-top: 1px solid var(--line);
  margin: 20px 0;
}
footer,
.footnote {
  font-size: 10px;
  color: var(--muted);
  margin-top: 18px;
}
.status {
  display: block;
  min-height: 20px;
  margin-top: 10px;
  color: var(--accent);
  font-size: 12px;
}
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
}
[hidden] {
  display: none !important;
}
.data-table {
  margin-top: 16px;
  font-size: 11px;
  color: var(--muted);
}
.data-table summary {
  cursor: pointer;
}
.table-scroll {
  overflow: auto;
  max-width: 100%;
}
table {
  border-collapse: collapse;
  width: 100%;
  font-size: 11px;
}
th,
td {
  text-align: left;
  border-bottom: 1px solid var(--line);
  padding: 9px;
  white-space: nowrap;
}
caption {
  text-align: left;
  color: var(--muted);
  padding: 8px 0;
}
.legend {
  display: flex;
  gap: 17px;
  flex-wrap: wrap;
  font-size: 11px;
  color: var(--muted);
}
.legend i {
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--c);
  margin-right: 6px;
}
dialog {
  max-width: calc(100vw - 36px);
  width: 460px;
  background: var(--panel);
  color: var(--text);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 25px;
}
dialog::backdrop {
  background: #000a;
}
dialog p {
  margin: 12px 0;
}
.media-credit {
  font-size: 9px;
  margin-top: 16px;
  color: var(--muted);
}
.stage {
  position: relative;
  min-height: 290px;
  border-radius: 18px;
  overflow: hidden;
  border: 1px solid var(--line);
  background: var(--panel);
}
@media (max-width: 520px) {
  .intro {
    align-items: flex-start;
    flex-direction: column;
  }
  .grid {
    grid-template-columns: 1fr;
  }
  .panel {
    padding: 17px;
  }
  .toolbar label {
    flex-wrap: wrap;
  }
  .stage {
    min-height: 270px;
  }
  h1 {
    font-size: 32px;
  }
  .intro p {
    font-size: 12px;
  }
}
@media (prefers-reduced-motion: reduce) {
  *,
  *:before,
  *:after {
    animation: none !important;
    transition: none !important;
    scroll-behavior: auto !important;
  }
}
html {
  color-scheme: dark;
}
#chart {
  width: 100%;
  height: auto;
  overflow: visible;
}
#chart text {
  font-family: system-ui, sans-serif;
  fill: var(--muted);
  font-size: 11px;
}
.chart-summary {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 15px;
}
.chart-summary strong {
  font-size: 33px;
  letter-spacing: -1.4px;
}
.chart-summary span {
  font-size: 11px;
  color: var(--muted);
}
.curve-controls {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 15px;
  margin: 10px 0;
}
.curve-controls label {
  font:
    10px ui-monospace,
    monospace;
  display: grid;
  grid-template-columns: 24px 1fr 25px;
  gap: 10px;
}
#path-code {
  display: block;
  color: var(--accent);
  font-size: 11px;
  overflow-wrap: anywhere;
  background: var(--bg);
  padding: 12px;
  border-radius: 8px;
}
@media (max-width: 430px) {
  .curve-controls {
    grid-template-columns: 1fr;
  }
}

(() => {
  "use strict";
  const $ = (s) => document.querySelector(s),
    $$ = (s) => [...document.querySelectorAll(s)],
    status = (t) => {
      const el = $("#status");
      if (el) el.textContent = t;
    },
    clamp = (n, a, b) => Math.max(a, Math.min(b, n));
  const reduced = matchMedia("(prefers-reduced-motion: reduce)").matches;
  const ns = "http://www.w3.org/2000/svg";
  function svg(tag, attrs = {}, text) {
    const el = document.createElementNS(ns, tag);
    for (const [k, v] of Object.entries(attrs)) el.setAttribute(k, String(v));
    if (text !== undefined) el.textContent = text;
    return el;
  }
  function table(headers, rows) {
    const t = $("#data-table");
    if (!t) return;
    t.replaceChildren();
    const caption = document.createElement("caption");
    caption.textContent = "Illustrative sample data";
    t.append(caption);
    const head = t.createTHead().insertRow();
    headers.forEach((v) => {
      const th = document.createElement("th");
      th.scope = "col";
      th.textContent = v;
      head.append(th);
    });
    const body = t.createTBody();
    rows.forEach((row) => {
      const r = body.insertRow();
      row.forEach((v) => (r.insertCell().textContent = String(v)));
    });
  }
  function selectButtons(selector, callback) {
    $$(selector).forEach((b) =>
      b.addEventListener("click", () => {
        $$(selector).forEach((x) => x.setAttribute("aria-pressed", String(x === b)));
        callback(b);
      }),
    );
  }

  let variant = 0;
  function draw() {
    const v = {};
    $$("[data-control]").forEach((i) => {
      v[i.dataset.control] = Number(i.value);
      $("#out-" + i.dataset.control).textContent = i.value;
    });
    const path = "M 45 135 C " + v.x1 + " " + v.y1 + ", " + v.x2 + " " + v.y2 + ", 655 135";
    const s = $("#chart");
    s.replaceChildren();
    for (let x = 0; x <= 700; x += 35)
      s.append(svg("path", { d: "M" + x + " 0V270", stroke: "var(--line)", "stroke-width": 0.5 }));
    for (let y = 0; y <= 270; y += 30)
      s.append(svg("path", { d: "M0 " + y + "H700", stroke: "var(--line)", "stroke-width": 0.5 }));
    s.append(
      svg("path", {
        d: "M45 135L" + v.x1 + " " + v.y1 + "M655 135L" + v.x2 + " " + v.y2,
        stroke: "#c5a4ff",
        "stroke-dasharray": "5 5",
        fill: "none",
      }),
    );
    s.append(svg("path", { d: path, stroke: "var(--accent)", "stroke-width": 4, fill: "none" }));
    [
      [45, 135, "START"],
      [v.x1, v.y1, "P1"],
      [v.x2, v.y2, "P2"],
      [655, 135, "END"],
    ].forEach(([x, y, t]) => {
      s.append(
        svg("circle", {
          cx: x,
          cy: y,
          r: 6,
          fill: t.startsWith("P") ? "#c5a4ff" : "var(--accent)",
        }),
      );
      s.append(svg("text", { x: clamp(x + 12, 5, 655), y: clamp(y - 12, 14, 255) }, t));
    });
    $("#path-code").textContent = 'd="' + path + '"';
  }
  $$("[data-control]").forEach((i) => i.addEventListener("input", draw));
  function preset(vals) {
    $$("[data-control]").forEach((i, n) => (i.value = vals[n]));
    draw();
  }
  $("#change").addEventListener("click", () => {
    const presets = [
      [220, 260, 450, 10],
      [610, 10, 80, 260],
      [160, 30, 520, 230],
    ];
    preset(presets[variant++ % 3]);
    status("Curve variation " + variant + " applied. The path coordinates are ready to copy.");
  });
  $("#reset").addEventListener("click", () => {
    preset([160, 30, 520, 230]);
    status("Control points reset.");
  });
  draw();
})();