diff --git a/src/lib/components/organisms/Footer.svelte b/src/lib/components/organisms/Footer.svelte
index 6bc354f..7c53dac 100644
--- a/src/lib/components/organisms/Footer.svelte
+++ b/src/lib/components/organisms/Footer.svelte
@@ -25,11 +25,21 @@
 				{ label: 'Good first issues', href: 'https://github.com/langx/langx/contribute' },
 				{ label: 'Releases', href: 'https://github.com/langx/langx/releases' },
 				{ label: 'Docs', href: 'https://docs.langx.io' },
-				{ label: 'Word lists', href: '/tools/most-common-words' },
 				{ label: 'Status', href: 'https://status.langx.io' },
 				{ label: 'Branding', href: 'https://github.com/langx/branding' }
 			]
 		},
+		{
+			title: 'Tools',
+			links: [
+				{ label: 'All tools', href: '/tools' },
+				{ label: 'Word lists', href: '/tools/most-common-words' },
+				{ label: 'Say it in any language', href: '/tools/say' },
+				{ label: 'Vocabulary test', href: '/tools/vocabulary-test' },
+				{ label: 'Alphabets', href: '/tools/alphabet' },
+				{ label: 'Languages that overlap', href: '/tools/similar' }
+			]
+		},
 		{
 			title: 'Community',
 			links: [
@@ -171,7 +181,11 @@
 
 	.groups {
 		display: grid;
-		grid-template-columns: repeat(4, minmax(0, 1fr));
+		// Was a fixed four, which left the fifth group stranded alone on a second
+		// row. Five will not fit across the space the brand column leaves — the
+		// labels here are longer than "Legal" — so three and two, which reads as
+		// a layout rather than an accident.
+		grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
 		gap: var(--space-lg) var(--space-md);
 
 		@include for-phone-only {
diff --git a/src/lib/components/organisms/OpenSource.svelte b/src/lib/components/organisms/OpenSource.svelte
new file mode 100644
index 0000000..59effdf
--- /dev/null
+++ b/src/lib/components/organisms/OpenSource.svelte
@@ -0,0 +1,167 @@
+<script lang="ts">
+	import { onMount } from 'svelte';
+	import Button from '$lib/components/atoms/Button.svelte';
+	import GithubIcon from '$lib/icons/socials/github.svelte';
+
+	/**
+	 * The open-source chapter. Every line here is a fact somebody can check in a
+	 * minute, which is the only kind of claim this section is allowed to make:
+	 * the licence file, the repository, the self-hosting guide.
+	 *
+	 * Deliberately says nothing about tracking or analytics. The app ships a
+	 * product-analytics SDK, so a "no trackers" line here would be false — see
+	 * the note in PRODUCT.md.
+	 */
+	const repo = 'langx/langx';
+	let stars = -1;
+
+	onMount(async () => {
+		try {
+			const res = await fetch(`https://api.github.com/repos/${repo}`);
+			if (!res.ok) return;
+			stars = (await res.json()).stargazers_count ?? -1;
+		} catch {
+			// Rate-limited or offline. The count is decoration; the facts are not.
+		}
+	});
+
+	const facts = [
+		{ big: 'BSD-3', small: 'licensed — use it, fork it, sell it' },
+		{ big: 'Every line', small: 'of the app and the API, in the open' },
+		{ big: 'Self-hostable', small: 'run the whole thing on your own server' }
+	];
+</script>
+
+<section class="os">
+	<div class="container">
+		<h2>open source. all of it.</h2>
+		<p class="lede">
+			Not a public mirror, not an SDK, not the client with the interesting half missing. The app you
+			install and the server it talks to are the same code you can read, change and run yourself.
+		</p>
+
+		<dl class="facts">
+			{#each facts as f}
+				<div>
+					<dt>{f.big}</dt>
+					<dd>{f.small}</dd>
+				</div>
+			{/each}
+		</dl>
+
+		<div class="actions">
+			<Button href="https://github.com/{repo}" variant="secondary" size="md">
+				<span class="gh"><GithubIcon /></span>
+				Read the source
+				{#if stars > 0}<span class="stars">{stars.toLocaleString('en-US')}</span>{/if}
+			</Button>
+			<a class="ghost" href="https://github.com/langx/langx/contribute">Good first issues</a>
+		</div>
+	</div>
+</section>
+
+<style lang="scss">
+	@import '$lib/scss/breakpoints.scss';
+
+	.os {
+		border-top: 1px solid var(--color--border);
+		padding: var(--space-3xl) 0;
+
+		@include for-phone-only {
+			padding: var(--space-2xl) 0;
+		}
+	}
+
+	// The chapter voice: lowercase, ending in a full stop. Ink rather than blue,
+	// because there is no phone beside it.
+	h2 {
+		font-family: var(--font--title);
+		font-weight: 800;
+		font-size: clamp(2rem, 1.4rem + 2.4vw, 3rem);
+		line-height: 1.05;
+		letter-spacing: -0.02em;
+		max-width: 16ch;
+	}
+
+	.lede {
+		font-size: 1.125rem;
+		line-height: 1.6;
+		color: var(--color--text-shade);
+		max-width: 52ch;
+		margin-top: var(--space-sm);
+	}
+
+	// Hairlines and figures, not cards — the same device the tools pages use.
+	.facts {
+		display: grid;
+		grid-template-columns: repeat(3, minmax(0, 1fr));
+		border-top: 1px solid var(--color--border);
+		border-bottom: 1px solid var(--color--border);
+		margin: var(--space-xl) 0 var(--space-lg);
+
+		> div {
+			padding: var(--space-md) var(--space-md) var(--space-md) 0;
+
+			+ div {
+				border-left: 1px solid var(--color--border);
+				padding-left: var(--space-md);
+			}
+		}
+
+		dt {
+			font-family: var(--font--title);
+			font-weight: 800;
+			font-size: clamp(1.375rem, 1.1rem + 1.1vw, 1.875rem);
+			line-height: 1.1;
+			letter-spacing: -0.02em;
+		}
+
+		dd {
+			margin-top: var(--space-2xs);
+			font-size: 0.8125rem;
+			line-height: 1.4;
+			color: var(--color--text-quiet);
+			max-width: 24ch;
+		}
+
+		@include for-phone-only {
+			grid-template-columns: 1fr;
+
+			> div + div {
+				border-left: 0;
+				padding-left: 0;
+				border-top: 1px solid var(--color--border);
+			}
+		}
+	}
+
+	.actions {
+		display: flex;
+		flex-wrap: wrap;
+		align-items: center;
+		gap: var(--space-sm);
+	}
+
+	.gh {
+		display: inline-flex;
+		width: 18px;
+		height: 18px;
+	}
+
+	.stars {
+		font-variant-numeric: tabular-nums;
+		color: var(--color--text-quiet);
+	}
+
+	.ghost {
+		color: var(--color--accent);
+		font-size: 0.9375rem;
+		font-weight: 600;
+		padding: 0 10px;
+	}
+
+	// No scroll reveal here, deliberately. The other chapters fade in because
+	// what they hold is a demonstration; this one holds claims about the licence
+	// and the source, and a claim that depends on an IntersectionObserver firing
+	// is a claim that can fail to appear at all.
+</style>
diff --git a/src/routes/(site)/+page.svelte b/src/routes/(site)/+page.svelte
index c2483d5..5fd2325 100644
--- a/src/routes/(site)/+page.svelte
+++ b/src/routes/(site)/+page.svelte
@@ -4,6 +4,7 @@
 	import LanguageMarquee from '$lib/components/organisms/LanguageMarquee.svelte';
 	import Story from '$lib/components/organisms/Story.svelte';
 	import Anywhere from '$lib/components/organisms/Anywhere.svelte';
+	import OpenSource from '$lib/components/organisms/OpenSource.svelte';
 	import Testimonials from '$lib/components/organisms/Testimonials.svelte';
 	import Faq from '$lib/components/organisms/FAQ.svelte';
 	import FinalCta from '$lib/components/organisms/FinalCta.svelte';
@@ -16,6 +17,7 @@
 	<LanguageMarquee />
 	<Story />
 	<Anywhere />
+	<OpenSource />
 	<Testimonials />
 	<Faq />
 	<FinalCta />
diff --git a/src/routes/(site)/tools/vocabulary-test/+page.svelte b/src/routes/(site)/tools/vocabulary-test/+page.svelte
new file mode 100644
index 0000000..01ad053
--- /dev/null
+++ b/src/routes/(site)/tools/vocabulary-test/+page.svelte
@@ -0,0 +1,138 @@
+<script lang="ts">
+	import Seo from '$lib/components/atoms/Seo.svelte';
+	import ScriptDisc from '$lib/components/atoms/ScriptDisc.svelte';
+	import PageHeader from '$lib/components/organisms/PageHeader.svelte';
+	import { WORD_LISTS } from '$lib/data/most-common-words';
+
+	const nf = new Intl.NumberFormat('en-US');
+	const POPULAR = ['es', 'fr', 'de', 'it', 'pt', 'ru', 'tr', 'zh', 'ko', 'ar', 'nl', 'pl'];
+	const popular = POPULAR.map((c) => WORD_LISTS.find((l) => l.code === c)).filter(
+		Boolean
+	) as typeof WORD_LISTS;
+</script>
+
+<Seo
+	title="Vocabulary tests"
+	path="/tools/vocabulary-test"
+	description="Find out roughly how many words you know, in any of {WORD_LISTS.length} languages. Forty-two words, two minutes, no account."
+/>
+
+<div class="container">
+	<PageHeader
+		title="How many words do you know?"
+		lede="Forty-two words drawn from across the whole frequency range — the commonest through to the
+		rare. Mark the ones you know and see roughly how much of the language that covers. Two minutes, no
+		account, and the result is a link you can keep."
+	/>
+
+	<section class="block">
+		<h2>Start here</h2>
+		<ul class="popular" role="list">
+			{#each popular as l}
+				<li>
+					<a href="/tools/vocabulary-test/{l.slug}">
+						<ScriptDisc nativeName={l.nativeName} code={l.code} size={44} />
+						<span class="names">
+							<span class="native" lang={l.code}>{l.nativeName}</span>
+							<span class="english">{l.name}</span>
+						</span>
+					</a>
+				</li>
+			{/each}
+		</ul>
+	</section>
+
+	<section class="block">
+		<h2>All {WORD_LISTS.length} languages</h2>
+		<ul class="rows" role="list">
+			{#each WORD_LISTS as l}
+				<li>
+					<a href="/tools/vocabulary-test/{l.slug}">
+						<ScriptDisc nativeName={l.nativeName} code={l.code} size={30} />
+						<span class="lang">{l.name}</span>
+						<span class="n tabular">{nf.format(l.count)} words</span>
+					</a>
+				</li>
+			{/each}
+		</ul>
+	</section>
+</div>
+
+<style lang="scss">
+	@import '$lib/scss/breakpoints.scss';
+
+	.block {
+		padding: var(--space-xl) 0 0;
+
+		h2 {
+			font-family: var(--font--title);
+			font-weight: 800;
+			font-size: clamp(1.75rem, 1.3rem + 1.6vw, 2.375rem);
+			letter-spacing: -0.015em;
+			margin-bottom: var(--space-sm);
+		}
+	}
+
+	.popular {
+		display: grid;
+		grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
+		gap: 0 var(--space-lg);
+		border-top: 1px solid var(--color--border);
+
+		li {
+			border-bottom: 1px solid var(--color--border);
+		}
+
+		a {
+			display: flex;
+			align-items: center;
+			gap: var(--space-xs);
+			padding: 14px 0;
+			color: var(--color--text);
+		}
+
+		.names {
+			display: flex;
+			flex-direction: column;
+			min-width: 0;
+		}
+
+		.native {
+			font-family: var(--font--title);
+			font-weight: 800;
+			font-size: 1.125rem;
+		}
+
+		.english {
+			font-size: 0.8125rem;
+			color: var(--color--text-quiet);
+		}
+	}
+
+	.rows {
+		border-top: 1px solid var(--color--border);
+
+		li {
+			border-bottom: 1px solid var(--color--border);
+		}
+
+		a {
+			display: flex;
+			align-items: center;
+			gap: var(--space-sm);
+			padding: 13px 0;
+			color: var(--color--text);
+		}
+	}
+
+	.lang {
+		font-family: var(--font--title);
+		font-weight: 800;
+	}
+
+	.n {
+		margin-left: auto;
+		color: var(--color--text-quiet);
+		font-size: 0.8125rem;
+	}
+</style>