> ## Documentation Index
> Fetch the complete documentation index at: https://hyperframes-fix-nested-composition-media-inpoint.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Code Highlight Sweep

> A highlight band sweeps across a target line while the surrounding context dims — draws the eye to one line.

export const InstallCommand = ({command, item}) => {
  const [copied, setCopied] = React.useState(false);
  const [tuned, setTuned] = React.useState("");
  React.useEffect(() => {
    if (!item) return;
    const read = () => {
      try {
        const raw = new URLSearchParams(window.location.search).get(`vars-${item}`);
        if (!raw) return setTuned("");
        const parsed = JSON.parse(raw);
        if (!parsed || typeof parsed !== "object" || Array.isArray(parsed)) return setTuned("");
        if (Object.keys(parsed).length === 0) return setTuned("");
        setTuned(` --vars '${JSON.stringify(parsed)}'`);
      } catch {
        setTuned("");
      }
    };
    read();
    window.addEventListener("hf-vars-changed", read);
    window.addEventListener("popstate", read);
    return () => {
      window.removeEventListener("hf-vars-changed", read);
      window.removeEventListener("popstate", read);
    };
  }, [item]);
  const fullCommand = `${command}${tuned}`;
  const copy = async () => {
    try {
      if (navigator.clipboard && window.isSecureContext) {
        await navigator.clipboard.writeText(fullCommand);
      } else {
        const previous = document.activeElement;
        const scratch = document.createElement("textarea");
        scratch.value = fullCommand;
        scratch.setAttribute("readonly", "");
        scratch.style.position = "fixed";
        scratch.style.opacity = "0";
        document.body.appendChild(scratch);
        scratch.select();
        document.execCommand("copy");
        document.body.removeChild(scratch);
        previous?.focus?.();
      }
      setCopied(true);
      setTimeout(() => setCopied(false), 2000);
    } catch {}
  };
  return <div className="hf-install-command not-prose my-4 flex items-stretch overflow-hidden rounded-xl border border-zinc-200 bg-zinc-50 dark:border-zinc-800 dark:bg-zinc-900">
      <code className="flex-1 overflow-x-auto whitespace-nowrap border-r border-zinc-200 px-4 py-3 font-mono text-sm text-zinc-800 dark:border-zinc-800 dark:text-zinc-100">
        {fullCommand}
      </code>
      <button type="button" onClick={copy} data-copied={copied ? "true" : "false"} aria-label={`Copy ${command} to the clipboard`} className="hf-install-copy">
        <svg className="hf-install-copy-clipboard" xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 18 18" fill="none" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true">
          <path d="M14.25 5.25H7.25C6.14543 5.25 5.25 6.14543 5.25 7.25V14.25C5.25 15.3546 6.14543 16.25 7.25 16.25H14.25C15.3546 16.25 16.25 15.3546 16.25 14.25V7.25C16.25 6.14543 15.3546 5.25 14.25 5.25Z" />
          <path d="M2.80103 11.998L1.77203 5.07397C1.61003 3.98097 2.36403 2.96397 3.45603 2.80197L10.38 1.77297C11.313 1.63397 12.19 2.16297 12.528 3.00097" />
        </svg>
        <svg className="hf-install-copy-check" xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 18 18" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true">
          <path d="M2.75 9.5L6.5 13.25L15.25 4.5" />
        </svg>
      </button>
      <span className="hf-install-copy-status" role="status" aria-live="polite">
        {copied ? "Copied" : ""}
      </span>
    </div>;
};

<iframe className="w-full aspect-video rounded-xl border-0 bg-zinc-100 dark:bg-zinc-800" title="code-highlight preview" loading="lazy" srcDoc={`<!doctype html><html><head><meta charset="utf-8"><style>html,body{margin:0;height:100%;overflow:hidden;background:transparent}hyperframes-player{display:block;width:100%;height:100%}</style><script src="https://cdn.jsdelivr.net/npm/@hyperframes/player@0.7/dist/hyperframes-player.global.js"><\/script></head><body><script>fetch("/public/catalog/blocks/code-highlight.json").then(function(r){return r.json()}).then(function(d){var p=document.createElement("hyperframes-player");p.setAttribute("srcdoc",d.html);p.setAttribute("controls","");p.setAttribute("autoplay","");p.setAttribute("loop","");p.setAttribute("muted","");p.setAttribute("poster","https://static.heygen.ai/hyperframes-oss/docs/images/catalog/blocks/code-highlight.png");document.body.appendChild(p)});<\/script></body></html>`} />

## Install

<InstallCommand command="npx hyperframes add code-highlight" item="code-highlight" />

That writes one file: `compositions/code-highlight.html`.

## Source

<Accordion title={`code-highlight.html`}>
  ```html theme={null}
  <!doctype html>
  <html lang="en">
    <head>
      <meta charset="UTF-8" />
      <meta name="viewport" content="width=1920, height=1080" />
      <title>Code Highlight Sweep</title>
      <script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
      <style>
        * {
          margin: 0;
          padding: 0;
          box-sizing: border-box;
        }
        html,
        body {
          width: 1920px;
          height: 1080px;
          overflow: hidden;
          background: #05070b;
        }
        #root {
          position: relative;
          width: 1920px;
          height: 1080px;
          font-family: "JetBrains Mono", monospace;
          color: #e6edf3;
        }
        .bg-field {
          position: absolute;
          inset: 0;
          background: radial-gradient(1200px 700px at 50% 18%, #0e1726 0%, #070b12 55%, #05070b 100%);
        }
        .bg-grid {
          position: absolute;
          inset: 0;
          background-image:
            linear-gradient(rgba(88, 166, 255, 0.05) 1px, transparent 1px),
            linear-gradient(90deg, rgba(88, 166, 255, 0.05) 1px, transparent 1px);
          background-size: 64px 64px;
          mask-image: radial-gradient(1100px 620px at 50% 42%, #000 0%, transparent 78%);
        }
        .bg-glow {
          position: absolute;
          width: 900px;
          height: 900px;
          border-radius: 50%;
          filter: blur(120px);
          opacity: 0.5;
        }
        .bg-glow.a {
          background: #1f6feb55;
          left: -180px;
          top: -200px;
        }
        .bg-glow.b {
          background: #2ea04355;
          right: -200px;
          bottom: -260px;
        }
        .editor {
          position: absolute;
          left: 50%;
          top: 50%;
          transform: translate(-50%, -50%);
          width: 1380px;
          height: 800px;
          background: #0b0f17;
          border: 1px solid #1d2733;
          border-radius: 16px;
          box-shadow:
            0 40px 120px rgba(0, 0, 0, 0.6),
            0 2px 0 rgba(255, 255, 255, 0.03) inset;
          overflow: hidden;
          display: flex;
          flex-direction: column;
        }
        .titlebar {
          height: 56px;
          flex: 0 0 56px;
          display: flex;
          align-items: center;
          gap: 16px;
          padding: 0 22px;
          background: linear-gradient(#11161f, #0c111a);
          border-bottom: 1px solid #1b2430;
        }
        .dots {
          display: flex;
          gap: 10px;
        }
        .dot {
          width: 14px;
          height: 14px;
          border-radius: 50%;
        }
        .dot.r {
          background: #ff5f57;
        }
        .dot.y {
          background: #febc2e;
        }
        .dot.g {
          background: #28c840;
        }
        .filename {
          font-size: 19px;
          color: #8b98a9;
          letter-spacing: 0.2px;
        }
        .filename .accent {
          color: #d6e2f0;
        }
        .code-surface {
          position: relative;
          flex: 1 1 auto;
          overflow: hidden;
        }
        .scene {
          position: absolute;
          inset: 0;
          opacity: 0;
          will-change: opacity;
        }
        .code {
          position: absolute;
          top: 38px;
          left: 0;
          right: 0;
          padding: 0 44px 0 104px;
          font-size: 30px;
          line-height: 46px;
          font-variant-ligatures: none;
          tab-size: 2;
        }
        .gutter {
          position: absolute;
          top: 38px;
          left: 0;
          width: 84px;
          padding-right: 18px;
          font-size: 30px;
          line-height: 46px;
          text-align: right;
          color: #828c9b;
          user-select: none;
        }
        .ln {
          display: block;
          height: 46px;
        }
        .line {
          display: block;
          min-height: 46px;
          white-space: pre;
          position: relative;
          z-index: 1;
        }
        .tok {
          display: inline-block;
          white-space: pre;
          will-change: transform, opacity;
        }
        .caret {
          position: absolute;
          top: 0;
          left: 0;
          width: 3px;
          height: 32px;
          margin-top: 6px;
          background: #58a6ff;
          border-radius: 1px;
          z-index: 3;
        }
        .hl-box {
          position: absolute;
          background: rgba(88, 166, 255, 0.16);
          border-left: 3px solid #58a6ff;
          border-radius: 6px;
          z-index: 0;
          overflow: hidden;
        }
        .diff-line {
          display: block;
          min-height: 0;
          line-height: 46px;
          white-space: pre;
          position: relative;
          overflow: hidden;
          padding-left: 14px;
        }
        .diff-sign {
          display: inline-block;
          width: 22px;
          color: #41506220;
        }
        .diff-del {
          background: rgba(248, 81, 73, 0.12);
          box-shadow: inset 3px 0 #f85149;
        }
        .diff-add {
          background: rgba(63, 185, 80, 0.12);
          box-shadow: inset 3px 0 #3fb950;
        }
        .diff-del .diff-sign {
          color: #f85149;
        }
        .diff-add .diff-sign {
          color: #3fb950;
        }
        .flight-block {
          position: absolute;
          white-space: pre;
          font-size: 27px;
          line-height: 40px;
          padding: 11px 22px;
          border-radius: 11px;
          background: #0f1722;
          border: 1px solid #233044;
          box-shadow: 0 16px 44px rgba(0, 0, 0, 0.5);
          will-change: transform, opacity;
        }
        .flight-target {
          position: absolute;
          border: 1.5px dashed #2a3a4f;
          border-radius: 14px;
          opacity: 0;
        }
      </style>
    </head>
    <body>
      <div
        id="root"
        data-composition-id="code-highlight"
        data-start="0"
        data-duration="5"
        data-width="1920"
        data-height="1080"
      >
        <div class="bg-field" data-layout-ignore></div>
        <div class="bg-grid" data-layout-ignore></div>
        <div class="bg-glow a" data-layout-ignore></div>
        <div class="bg-glow b" data-layout-ignore></div>
        <div class="editor" id="editor" data-layout-ignore>
          <div class="titlebar">
            <div class="dots">
              <span class="dot r"></span><span class="dot y"></span><span class="dot g"></span>
            </div>
            <span class="filename"
              ><span class="accent">loadConfig.js</span> — Code Highlight Sweep</span
            >
          </div>
          <div class="code-surface" id="surface"></div>
        </div>
      </div>
      <script>
        window.__TOKENS = {
          feature: {
            lang: "js",
            theme: "github-dark",
            bg: "#24292e",
            fg: "#e1e4e8",
            states: [
              {
                code: 'async function loadConfig(path) {\n  const raw = await readFile(path, "utf8")\n  const config = JSON.parse(raw)\n  return validate(config)\n}',
                tokens: [
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-0",
                    content: "async",
                    color: "#F97583",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-1",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-2",
                    content: "function",
                    color: "#F97583",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-3",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-4",
                    content: "loadConfig",
                    color: "#B392F0",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-5",
                    content: "(",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-6",
                    content: "path",
                    color: "#FFAB70",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-7",
                    content: ") {",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-8",
                    content: "\n",
                    color: "#e1e4e8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-9",
                    content: "  ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-10",
                    content: "const",
                    color: "#F97583",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-11",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-12",
                    content: "raw",
                    color: "#79B8FF",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-13",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-14",
                    content: "=",
                    color: "#F97583",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-15",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-16",
                    content: "await",
                    color: "#F97583",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-17",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-18",
                    content: "readFile",
                    color: "#B392F0",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-19",
                    content: "(path,",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-20",
                    content: " ",
                    color: "#e1e4e8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-21",
                    content: '"utf8"',
                    color: "#9ECBFF",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-22",
                    content: ")",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-23",
                    content: "\n",
                    color: "#e1e4e8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-24",
                    content: "  ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-25",
                    content: "const",
                    color: "#F97583",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-26",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-27",
                    content: "config",
                    color: "#79B8FF",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-28",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-29",
                    content: "=",
                    color: "#F97583",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-30",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-31",
                    content: "JSON",
                    color: "#79B8FF",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-32",
                    content: ".",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-33",
                    content: "parse",
                    color: "#B392F0",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-34",
                    content: "(raw)",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-35",
                    content: "\n",
                    color: "#e1e4e8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-36",
                    content: "  ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-37",
                    content: "return",
                    color: "#F97583",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-38",
                    content: " ",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-39",
                    content: "validate",
                    color: "#B392F0",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-40",
                    content: "(config)",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-41",
                    content: "\n",
                    color: "#e1e4e8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-42",
                    content: "}",
                    color: "#E1E4E8",
                    fontStyle: 0,
                  },
                  {
                    key: "SPx9u4TyzfMqSHpbjPHnWFQU8lPVEPieF6W5Vtu-bNA-43",
                    content: "\n",
                    color: "#e1e4e8",
                    fontStyle: 0,
                  },
                ],
              },
            ],
          },
        };
        window.__BLOCK = {
          id: "code-highlight",
          effect: "highlight",
          seq: "feature",
          line: 1,
          duration: 5,
        };
      </script>
      <script>
        // hf-code-anim.js — self-contained code-animation engine for HyperFrames registry blocks.
        //
        // Reuses Shiki Magic Move's baked output (window.__TOKENS, baked at author time) and
        // drives the animation as a PAUSED GSAP timeline the HyperFrames engine seeks per frame —
        // NOT CSS transitions (those break under non-sequential frame seeking). FLIP measurement
        // runs once inside document.fonts.ready (glyph metrics must be final). Each block sets
        // window.__BLOCK = { id, effect, seq, line?, duration } and includes this engine; the
        // engine builds one scene that fills the composition and registers window.__timelines[id].
        (function () {
          "use strict";
          var T = window.__TOKENS || {};

          function lineDiv() {
            var d = document.createElement("div");
            d.className = "line";
            return d;
          }

          // Render a code state's keyed tokens into codeEl as lines of inline-block .tok spans.
          function renderState(codeEl, state) {
            codeEl.textContent = "";
            var keyToEl = new Map();
            var line = lineDiv();
            codeEl.appendChild(line);
            for (var i = 0; i < state.tokens.length; i++) {
              var t = state.tokens[i];
              if (t.content === "\n") {
                line = lineDiv();
                codeEl.appendChild(line);
                continue;
              }
              var span = document.createElement("span");
              span.className = "tok";
              span.textContent = t.content;
              span.style.color = t.color;
              if (t.fontStyle & 1) span.style.fontStyle = "italic";
              if (t.fontStyle & 2) span.style.fontWeight = "700";
              line.appendChild(span);
              keyToEl.set(t.key, span);
            }
            var last = codeEl.lastChild;
            if (last && last.className === "line" && last.children.length === 0)
              codeEl.removeChild(last);
            return keyToEl;
          }

          function rectsOf(keyToEl) {
            var m = new Map();
            keyToEl.forEach(function (el, k) {
              var r = el.getBoundingClientRect();
              m.set(k, { left: r.left, top: r.top });
            });
            return m;
          }

          function makeScene(surface, withGutter) {
            var scene = document.createElement("div");
            scene.className = "scene";
            if (withGutter) {
              var g = document.createElement("div");
              g.className = "gutter";
              scene.appendChild(g);
            }
            var code = document.createElement("div");
            code.className = "code";
            scene.appendChild(code);
            surface.appendChild(scene);
            return { scene: scene, code: code, gutter: scene.querySelector(".gutter") };
          }

          function fillGutter(g, n) {
            var html = "";
            for (var i = 1; i <= n; i++) html += '<span class="ln">' + i + "</span>";
            g.innerHTML = html;
          }

          function splitLines(state) {
            var lines = [{ text: "", tokens: [] }];
            for (var i = 0; i < state.tokens.length; i++) {
              var t = state.tokens[i];
              if (t.content === "\n") {
                lines.push({ text: "", tokens: [] });
                continue;
              }
              var cur = lines[lines.length - 1];
              cur.tokens.push(t);
              cur.text += t.content;
            }
            if (lines.length && lines[lines.length - 1].tokens.length === 0) lines.pop();
            return lines;
          }

          function lineDiff(a, b) {
            var n = a.length;
            var m = b.length;
            var dp = [];
            for (var i = 0; i <= n; i++) dp.push(new Array(m + 1).fill(0));
            for (var i = n - 1; i >= 0; i--) {
              for (var j = m - 1; j >= 0; j--) {
                dp[i][j] =
                  a[i].text === b[j].text
                    ? dp[i + 1][j + 1] + 1
                    : Math.max(dp[i + 1][j], dp[i][j + 1]);
              }
            }
            var ops = [];
            var i = 0;
            var j = 0;
            while (i < n && j < m) {
              if (a[i].text === b[j].text) {
                ops.push({ type: "same", line: b[j] });
                i++;
                j++;
              } else if (dp[i + 1][j] >= dp[i][j + 1]) {
                ops.push({ type: "del", line: a[i] });
                i++;
              } else {
                ops.push({ type: "add", line: b[j] });
                j++;
              }
            }
            while (i < n) ops.push({ type: "del", line: a[i++] });
            while (j < m) ops.push({ type: "add", line: b[j++] });
            return ops;
          }

          // ---- single-scene effect builders (fade in, play, hold to end) -------------
          var FADE = 0.45;

          function highlight(tl, surface, state, start, targetIdx) {
            var SWEEP = 0.9;
            var parts = makeScene(surface, true);
            var code = parts.code;
            renderState(code, state);
            var lines = code.querySelectorAll(".line");
            fillGutter(parts.gutter, lines.length);
            var base = code.getBoundingClientRect();
            var idx = Math.max(0, Math.min(lines.length - 1, targetIdx));
            var lr = lines[idx].getBoundingClientRect();
            var box = document.createElement("div");
            box.className = "hl-box";
            box.style.left = lr.left - base.left - 8 + "px";
            box.style.top = lr.top - base.top - 1 + "px";
            box.style.height = lr.height + 2 + "px";
            code.insertBefore(box, code.firstChild);
            tl.set(parts.scene, { opacity: 0 }, 0);
            tl.to(parts.scene, { opacity: 1, duration: FADE, ease: "power1.out" }, start);
            var at = start + FADE + 0.2;
            tl.fromTo(
              box,
              { width: 0, opacity: 0 },
              { width: lr.width + 18, opacity: 1, duration: SWEEP, ease: "power2.inOut" },
              at,
            );
            for (var i = 0; i < lines.length; i++) {
              if (i === idx) continue;
              tl.fromTo(
                lines[i],
                { opacity: 1 },
                { opacity: 0.45, duration: SWEEP, ease: "power2.inOut" },
                at,
              );
            }
          }

          function buildEffect(tl, surface, spec) {
            var start = 0.45;
            var seq = T[spec.seq];
            if (spec.effect === "highlight")
              highlight(tl, surface, seq.states[0], start, spec.line || 0);
          }

          function go() {
            var spec = window.__BLOCK;
            var surface = document.getElementById("surface");
            var root = document.getElementById("root");
            window.__timelines = window.__timelines || {};
            var tl = gsap.timeline({ paused: true });
            // Build inside fonts.ready (glyph metrics must be final), then register.
            // Register ONLY after the timeline is fully built: the runtime's
            // sub-composition readiness gate treats "key present" as "ready" and
            // nests the child once. An empty timeline registered before this build
            // would be nested empty and never re-nested → blank render when used as
            // a sub-composition. See the contract in engine frameCapture.ts.
            document.fonts.ready.then(function () {
              tl.from("#editor", { opacity: 0, scale: 0.985, duration: 0.5, ease: "power2.out" }, 0);
              buildEffect(tl, surface, spec);
              var dur = parseFloat(root.dataset.duration) || tl.duration();
              tl.to({}, { duration: dur }, 0); // pad to full composition length
              window.__timelines["code-highlight"] = tl; // register AFTER setup completes
              if (typeof window.__hfForceTimelineRebind === "function") {
                window.__hfForceTimelineRebind(); // re-nest now that we are populated
              }
            });
          }

          if (document.readyState === "loading") document.addEventListener("DOMContentLoaded", go);
          else go();
        })();
      </script>
    </body>
  </html>
  ```
</Accordion>

## Usage

After installing, add the block to your host composition:

```html theme={null}
<div data-composition-id="code-highlight" data-composition-src="compositions/code-highlight.html" data-start="0" data-duration="5" data-track-index="1" data-width="1920" data-height="1080"></div>
```

Tagged `code` `code-animation` `highlight` `developer`.

## Related topics

* [Browse the complete Catalog](/catalog)
* [Add assets and Catalog items in Studio](/studio/assets-and-blocks)
* [Build a richer composition](/go-further)
