diff --git a/marketing-site/components/reader/ChapterOutline.jsx b/marketing-site/components/reader/ChapterOutline.jsx
new file mode 100644
index 0000000..d7a8d08
--- /dev/null
+++ b/marketing-site/components/reader/ChapterOutline.jsx
@@ -0,0 +1,99 @@
+import { useEffect, useMemo, useState } from "react";
+
+function OutlineBody({ groups, complete, count, total, active, showTitle }) {
+  return (
+    <>
+      <p className="outline-progress">
+        {count}/{total} Try-its complete
+      </p>
+      {showTitle ? <p className="outline-heading">In this chapter</p> : null}
+      {groups.map((g) => (
+        <div key={g.label} className="outline-group">
+          <p className="outline-group-label spec">{g.label}</p>
+          <ul>
+            {g.items.map((item) => {
+              const done = item.recipeId ? !!complete[item.recipeId] : false;
+              const isActive = active === item.id;
+              return (
+                <li key={item.id}>
+                  <a
+                    href={`#${item.id}`}
+                    className={isActive ? "is-active" : undefined}
+                    aria-current={isActive ? "location" : undefined}
+                  >
+                    <span>{item.label}</span>
+                    {done ? (
+                      <span className="outline-done" aria-label="Try-it complete">
+                        ✓
+                      </span>
+                    ) : null}
+                  </a>
+                </li>
+              );
+            })}
+          </ul>
+        </div>
+      ))}
+    </>
+  );
+}
+
+export default function ChapterOutline({
+  groups,
+  complete = {},
+  count = 0,
+  total = 0,
+  variant = "desktop",
+}) {
+  const ids = useMemo(
+    () => groups.flatMap((g) => g.items.map((item) => item.id)),
+    [groups]
+  );
+  const [active, setActive] = useState(ids[0] || "");
+
+  useEffect(() => {
+    const els = ids.map((id) => document.getElementById(id)).filter(Boolean);
+    if (!els.length || typeof IntersectionObserver === "undefined") return;
+
+    const observer = new IntersectionObserver(
+      (entries) => {
+        const visible = entries
+          .filter((e) => e.isIntersecting)
+          .sort((a, b) => a.boundingClientRect.top - b.boundingClientRect.top);
+        if (visible[0]?.target?.id) setActive(visible[0].target.id);
+      },
+      { rootMargin: "-88px 0px -55% 0px", threshold: [0, 0.1, 0.25, 0.5, 1] }
+    );
+    els.forEach((el) => observer.observe(el));
+    return () => observer.disconnect();
+  }, [ids]);
+
+  if (variant === "mobile") {
+    return (
+      <details className="chapter-outline-mobile">
+        <summary>In this chapter</summary>
+        <OutlineBody
+          groups={groups}
+          complete={complete}
+          count={count}
+          total={total}
+          active={active}
+          showTitle={false}
+        />
+      </details>
+    );
+  }
+
+  return (
+    <nav className="chapter-outline" aria-label="In this chapter">
+      <OutlineBody
+        groups={groups}
+        complete={complete}
+        count={count}
+        total={total}
+        active={active}
+        showTitle
+      />
+    </nav>
+  );
+}