diff --git a/src/lib/components/CatalogGrid.svelte b/src/lib/components/CatalogGrid.svelte
index e9c8fdd..10a0899 100644
--- a/src/lib/components/CatalogGrid.svelte
+++ b/src/lib/components/CatalogGrid.svelte
@@ -9,7 +9,13 @@
 	import ProjectIcon from '#lib/components/ProjectIcon.svelte';
 	import TrackerIcon from '#lib/components/TrackerIcon.svelte';
 
-	type Item = { name: string; subtitle: string; href: string; external: boolean };
+	type Item = {
+		name: string;
+		subtitle: string;
+		href: string;
+		external: boolean;
+		children?: readonly Item[];
+	};
 	let {
 		items,
 		subtitleClass = 'mt-1 block text-sm text-muted-foreground',
@@ -60,9 +66,32 @@
 <ul class="grid gap-3 sm:grid-cols-2" class:wide>
 	{#each items as project (project.name)}
 		<li>
-			<Card.Root class="catalog-card h-full py-0 transition-colors hover:bg-muted/50"
+			<Card.Root class="catalog-card relative h-full py-0 transition-colors hover:bg-muted/50"
 				><Card.Content class="h-full p-0">
-					{#if project.external}
+					{#if project.children}
+						<!-- Group tile: a stretched main link plus direct links to each sub-tracker layered
+						     above it (siblings, so no nested <a>). -->
+						<div class="flex h-full min-h-28 flex-col gap-3 p-5">
+							<a
+								href={resolve(project.href as '/')}
+								class="stretched flex items-start justify-between gap-4 outline-none"
+							>
+								{@render body(project)}
+							</a>
+							<ul class="relative z-10 mt-auto flex flex-wrap gap-1.5 pl-13">
+								{#each project.children as child (child.name)}
+									<li>
+										<a
+											href={resolve(child.href as '/')}
+											class="chip flex items-center gap-1.5 py-1 pr-2.5 pl-1 text-xs font-medium"
+											title={child.subtitle}
+											><TrackerIcon name={child.name} class="chip-icon size-5" />{child.name}</a
+										>
+									</li>
+								{/each}
+							</ul>
+						</div>
+					{:else if project.external}
 						<a
 							href={project.href}
 							rel="external"
@@ -121,17 +150,57 @@
 	ul :global(.catalog-card:hover .catalog-arrow) {
 		transform: translateX(2px);
 	}
+	.stretched::after {
+		content: '';
+		position: absolute;
+		inset: 0;
+		border-radius: inherit;
+	}
+	.stretched:focus-visible::after {
+		outline: 2px solid var(--foreground);
+		outline-offset: -2px;
+	}
+	.chip {
+		border: 1px solid color-mix(in oklab, var(--foreground) 12%, transparent);
+		border-radius: 999px;
+		background: color-mix(in oklab, var(--background) 70%, transparent);
+		outline: none;
+		transition:
+			transform 160ms cubic-bezier(0.2, 0.8, 0.2, 1),
+			background-color 160ms ease,
+			border-color 160ms ease;
+	}
+	.chip:hover {
+		background: color-mix(in oklab, var(--foreground) 10%, transparent);
+		border-color: color-mix(in oklab, var(--foreground) 35%, transparent);
+		transform: translateY(-1px);
+	}
+	.chip:focus-visible {
+		outline: 2px solid var(--foreground);
+		outline-offset: 2px;
+	}
+	.chip :global(.chip-icon) {
+		border-radius: 999px;
+		transition: transform 160ms cubic-bezier(0.2, 0.8, 0.2, 1);
+	}
+	.chip:hover :global(.chip-icon) {
+		transform: scale(1.12);
+	}
 	@media (prefers-reduced-motion: reduce) {
 		ul :global(.catalog-card),
 		ul :global(.catalog-icon),
-		ul :global(.catalog-arrow) {
+		ul :global(.catalog-arrow),
+		.chip,
+		.chip :global(.chip-icon) {
 			transition:
 				background-color 160ms ease,
 				border-color 160ms ease;
 		}
 		ul :global(.catalog-card:hover),
 		ul :global(.catalog-card:hover .catalog-icon),
-		ul :global(.catalog-card:hover .catalog-arrow) {
+		ul :global(.catalog-card:hover .catalog-arrow),
+		.chip:hover,
+		.chip:hover :global(.chip-icon) {
 			transform: none;
 		}
 	}
diff --git a/src/lib/components/SiteChrome.svelte b/src/lib/components/SiteChrome.svelte
index d68c030..16c25c9 100644
--- a/src/lib/components/SiteChrome.svelte
+++ b/src/lib/components/SiteChrome.svelte
@@ -12,6 +12,7 @@
 	import * as Sheet from '#lib/components/ui/sheet/index.js';
 	import ArrowRight from 'lucide-svelte/icons/arrow-right';
 	import ChevronDown from 'lucide-svelte/icons/chevron-down';
+	import ChevronRight from 'lucide-svelte/icons/chevron-right';
 	import ExternalLink from 'lucide-svelte/icons/external-link';
 	import Menu from 'lucide-svelte/icons/menu';
 	import LayoutDashboard from 'lucide-svelte/icons/layout-dashboard';
@@ -51,7 +52,13 @@
 		{ label: 'blog', href: '/blog' },
 		{ label: 'lists', href: '/lists' }
 	] as const;
-	type MenuItem = { name: string; subtitle: string; href: string; external: boolean };
+	type MenuItem = {
+		name: string;
+		subtitle: string;
+		href: string;
+		external: boolean;
+		children?: readonly MenuItem[];
+	};
 	const menus: Record<string, { label: string; items: readonly MenuItem[] }> = $derived({
 		'/projects': { label: 'projects', items: projects },
 		'/trackers': { label: 'trackers', items: visibleTrackers(data.isOwner) }
@@ -168,6 +175,36 @@
 	function handleMenuPointerLeave(event: PointerEvent) {
 		if (event.pointerType === 'touch') return;
 		openMenu = null;
+		flyout = null;
+	}
+
+	// Group trackers (spotting) open a flyout with their sub-trackers next to their tile in the
+	// Trackers dropdown. It opens on hover or keyboard focus, on the outer side of the dropdown
+	// when there is room, and closes after a short delay so a diagonal mouse move from the tile
+	// into the flyout (crossing a neighbouring tile) does not close it.
+	let flyout = $state<string | null>(null);
+	let flyoutSide = $state<'left' | 'right'>('right');
+	let flyoutTimer: ReturnType<typeof setTimeout> | undefined;
+	const FLYOUT_WIDTH = 240;
+	function openFlyout(name: string, el: HTMLElement) {
+		clearTimeout(flyoutTimer);
+		if (flyout === name) return;
+		const rect = el.getBoundingClientRect();
+		const panel = el.closest('[data-menu-panel]')?.getBoundingClientRect() ?? rect;
+		const leftColumn = rect.left + rect.width / 2 < panel.left + panel.width / 2;
+		const roomLeft = rect.left - FLYOUT_WIDTH >= 8;
+		const roomRight = rect.right + FLYOUT_WIDTH <= window.innerWidth - 8;
+		flyoutSide = leftColumn ? (roomLeft ? 'left' : 'right') : roomRight ? 'right' : 'left';
+		flyout = name;
+	}
+	function closeFlyoutOnEscape(event: KeyboardEvent) {
+		if (event.key !== 'Escape' || !flyout) return;
+		event.stopPropagation();
+		flyout = null;
+	}
+	function closeFlyoutSoon() {
+		clearTimeout(flyoutTimer);
+		flyoutTimer = setTimeout(() => (flyout = null), 300);
 	}
 </script>
 
@@ -246,12 +283,14 @@
 							{#if openMenu === item.href}
 								<div
 									class={[
-										'absolute top-full z-50 max-h-[75vh] overflow-y-auto rounded-md border border-border bg-popover p-1 text-popover-foreground shadow-md',
+										'absolute top-full z-50 rounded-md border border-border bg-popover p-1 text-popover-foreground shadow-md',
+										// No overflow clipping on the trackers panel: its spotting flyout sticks out.
 										item.href === '/trackers'
 											? 'left-1/2 grid w-[min(36rem,calc(100vw-2rem))] -translate-x-1/2 grid-cols-2 gap-1.5 p-2'
-											: 'left-0 w-72'
+											: 'left-0 max-h-[75vh] w-72 overflow-y-auto'
 									]}
 									aria-label={menu.label}
+									data-menu-panel
 								>
 									<a
 										href={resolve(item.href)}
@@ -261,33 +300,106 @@
 									>
 									<div class="col-span-2 my-1 h-px bg-border"></div>
 									{#each menu.items as project (project.name)}
-										<!-- Internal project links use resolve; external URLs are from the project catalog. -->
-										<!-- eslint-disable svelte/no-navigation-without-resolve -->
-										<a
-											href={project.external ? project.href : resolve(project.href)}
-											rel={project.external ? 'external' : undefined}
-											class={item.href === '/trackers'
-												? 'tile flex items-center gap-2.5 p-2 text-sm'
-												: 'flex items-center gap-2 rounded-sm px-2 py-1.5 text-sm outline-none hover:bg-accent hover:text-accent-foreground focus-visible:bg-accent'}
-										>
-											{#if item.href === '/trackers'}
-												<TrackerIcon name={project.name} class="tile-icon size-9" />
-											{:else}
-												<span
-													class="flex size-8 shrink-0 items-center justify-center rounded border border-border bg-[var(--site-surface)] text-[var(--site-muted)]"
-												>
-													<ProjectIcon name={project.name} class="size-4" />
-												</span>
-											{/if}
-											<span class="min-w-0"
-												><span class="block font-medium">{project.name}</span><span
-													class="block truncate text-xs text-muted-foreground"
-													>{project.subtitle}</span
-												></span
+										{#if project.children}
+											<div
+												class="relative"
+												class:z-10={flyout === project.name}
+												role="group"
+												aria-label={`${project.name} trackers`}
+												onpointerenter={(event) => {
+													if (event.pointerType !== 'touch')
+														openFlyout(project.name, event.currentTarget);
+												}}
+												onpointerleave={(event) => {
+													if (event.pointerType !== 'touch') closeFlyoutSoon();
+												}}
+												onfocusin={(event) => openFlyout(project.name, event.currentTarget)}
+												onfocusout={(event) => {
+													if (!event.currentTarget.contains(event.relatedTarget as Node | null))
+														flyout = null;
+												}}
 											>
-											{#if project.external}<ExternalLink size={14} class="ml-auto shrink-0" />{/if}
-										</a>
-										<!-- eslint-enable svelte/no-navigation-without-resolve -->
+												<a
+													href={resolve(project.href as '/')}
+													class="tile flex h-full items-center gap-2.5 p-2 text-sm"
+													aria-haspopup="true"
+													onkeydown={closeFlyoutOnEscape}
+													aria-expanded={flyout === project.name}
+													><TrackerIcon name={project.name} class="tile-icon size-9" /><span
+														class="min-w-0"
+														><span class="block font-medium">{project.name}</span><span
+															class="block truncate text-xs text-muted-foreground"
+															>{project.subtitle}</span
+														></span
+													><ChevronRight
+														size={14}
+														class="ml-auto shrink-0 text-muted-foreground transition-transform {flyout ===
+														project.name
+															? flyoutSide === 'left'
+																? 'rotate-180'
+																: 'translate-x-0.5'
+															: ''}"
+													/></a
+												>
+												{#if flyout === project.name}
+													<!-- The padding facing the tile is a hover bridge into the panel. -->
+													<div
+														class={[
+															'absolute -top-2 w-60',
+															flyoutSide === 'right' ? 'left-full pl-3' : 'right-full pr-3'
+														]}
+													>
+														<div
+															class="flyout grid gap-1 rounded-md border border-border bg-popover p-1.5 shadow-lg"
+															class:from-left={flyoutSide === 'left'}
+														>
+															{#each project.children as child (child.name)}
+																<a
+																	href={resolve(child.href as '/')}
+																	class="tile flex items-center gap-2.5 p-1.5 text-sm"
+																	aria-current={current(child.href) ? 'page' : undefined}
+																	onkeydown={closeFlyoutOnEscape}
+																	><TrackerIcon name={child.name} class="tile-icon size-8" /><span
+																		class="font-medium">{child.name}</span
+																	></a
+																>
+															{/each}
+														</div>
+													</div>
+												{/if}
+											</div>
+										{:else}
+											<!-- Internal project links use resolve; external URLs are from the project catalog. -->
+											<!-- eslint-disable svelte/no-navigation-without-resolve -->
+											<a
+												href={project.external ? project.href : resolve(project.href)}
+												rel={project.external ? 'external' : undefined}
+												class={item.href === '/trackers'
+													? 'tile flex items-center gap-2.5 p-2 text-sm'
+													: 'flex items-center gap-2 rounded-sm px-2 py-1.5 text-sm outline-none hover:bg-accent hover:text-accent-foreground focus-visible:bg-accent'}
+											>
+												{#if item.href === '/trackers'}
+													<TrackerIcon name={project.name} class="tile-icon size-9" />
+												{:else}
+													<span
+														class="flex size-8 shrink-0 items-center justify-center rounded border border-border bg-[var(--site-surface)] text-[var(--site-muted)]"
+													>
+														<ProjectIcon name={project.name} class="size-4" />
+													</span>
+												{/if}
+												<span class="min-w-0"
+													><span class="block font-medium">{project.name}</span><span
+														class="block truncate text-xs text-muted-foreground"
+														>{project.subtitle}</span
+													></span
+												>
+												{#if project.external}<ExternalLink
+														size={14}
+														class="ml-auto shrink-0"
+													/>{/if}
+											</a>
+											<!-- eslint-enable svelte/no-navigation-without-resolve -->
+										{/if}
 									{/each}
 								</div>
 							{/if}
@@ -399,6 +511,23 @@
 											>
 											<!-- eslint-enable svelte/no-navigation-without-resolve -->
 										{/each}
+										{#each menus[item.href].items.filter((p) => p.children) as group (group.name)}
+											<div class="col-span-2 mt-1">
+												<span class="mb-1 block text-xs text-muted-foreground">{group.name}</span>
+												<div class="ml-1 grid grid-cols-2 gap-1.5 border-l border-border pl-2">
+													{#each group.children ?? [] as child (child.name)}
+														<a
+															href={resolve(child.href as '/')}
+															class="tile flex min-w-0 items-center gap-2 p-1.5 text-sm"
+															onclick={() => (menuOpen = false)}
+															><TrackerIcon name={child.name} class="tile-icon size-6" /><span
+																class="truncate">{child.name}</span
+															></a
+														>
+													{/each}
+												</div>
+											</div>
+										{/each}
 									</div>
 								{:else}
 									<div class="ml-3 flex flex-col border-l border-border pl-3">
@@ -533,6 +662,19 @@
 		background: color-mix(in oklab, var(--foreground) 9%, transparent);
 		border-color: color-mix(in oklab, var(--foreground) 35%, transparent);
 	}
+	.flyout {
+		animation: flyout-in 140ms cubic-bezier(0.2, 0.8, 0.2, 1);
+		--flyout-from: -4px;
+	}
+	.flyout.from-left {
+		--flyout-from: 4px;
+	}
+	@keyframes flyout-in {
+		from {
+			opacity: 0;
+			transform: translateX(var(--flyout-from));
+		}
+	}
 	.tile :global(.tile-icon) {
 		transition: transform 160ms cubic-bezier(0.2, 0.8, 0.2, 1);
 	}
@@ -555,6 +697,9 @@
 		background-image: linear-gradient(135deg, #10b981, #0d9488);
 	}
 	@media (prefers-reduced-motion: reduce) {
+		.flyout {
+			animation: none;
+		}
 		.tile,
 		.tile :global(.tile-icon) {
 			transition:
diff --git a/src/lib/projects.ts b/src/lib/projects.ts
index d88f4fe..6f7fc86 100644
--- a/src/lib/projects.ts
+++ b/src/lib/projects.ts
@@ -32,11 +32,51 @@ export const projects = [
 	}
 ] as const;
 
+type Tracker = {
+	name: string;
+	subtitle: string;
+	href: string;
+	external: boolean;
+	/** Sub-trackers linked directly from this item (header flyout, tile chips). */
+	children?: readonly Tracker[];
+};
+
+// The spotting trackers: pokedexes of things I can spot in the wild. Grouped under one
+// "spotting" item in the header, home page and /trackers; each keeps its own URL.
+export const spottingTrackers: readonly Tracker[] = [
+	{
+		name: 'cars',
+		subtitle: 'a car pokedex: every brand and model, with Dutch and US data',
+		href: '/trackers/cars',
+		external: false
+	},
+	{
+		name: 'trains',
+		subtitle:
+			'a train pokedex: steam, diesel and electric locos, high-speed trains, multiple units, metros and trams',
+		href: '/trackers/trains',
+		external: false
+	},
+	{
+		name: 'planes',
+		subtitle: 'a plane pokedex: airliners, helicopters, bizjets, light aircraft and warbirds',
+		href: '/trackers/planes',
+		external: false
+	},
+	{
+		name: 'wildlife',
+		subtitle:
+			'a wild animal pokedex: everything you can spot in the Netherlands, plus famous animals worldwide',
+		href: '/trackers/wildlife',
+		external: false
+	}
+];
+
 // Trackers, in display order. Names are short single nouns. Most keep their existing
 // /projects/... URLs (no moves, so no redirects needed). `private` trackers are shown in the
 // header, home page and /trackers only to the logged-in owner (layout data `isOwner`), never
 // in the sitemap; their routes 404 for everyone else.
-const allTrackers = [
+const allTrackers: readonly (Tracker & { private: boolean })[] = [
 	{
 		name: 'tasks',
 		subtitle: 'private: to-dos, goals and my TickTick history',
@@ -63,6 +103,7 @@ const allTrackers = [
 		subtitle: "cars, trains, planes & wildlife I've spotted",
 		href: '/trackers/spotting',
 		external: false,
+		children: spottingTrackers,
 		private: false
 	},
 	{
@@ -135,45 +176,10 @@ const allTrackers = [
 		external: false,
 		private: false
 	}
-] as const;
-
-type Tracker = { name: string; subtitle: string; href: string; external: boolean };
-const strip = ({ name, subtitle, href, external }: Tracker): Tracker => ({
-	name,
-	subtitle,
-	href,
-	external
-});
-// The spotting trackers: pokedexes of things I can spot in the wild. Grouped under one
-// "spotting" item in the header, home page and /trackers; each keeps its own URL.
-export const spottingTrackers: readonly Tracker[] = [
-	{
-		name: 'cars',
-		subtitle: 'a car pokedex: every brand and model, with Dutch and US data',
-		href: '/trackers/cars',
-		external: false
-	},
-	{
-		name: 'trains',
-		subtitle:
-			'a train pokedex: steam, diesel and electric locos, high-speed trains, multiple units, metros and trams',
-		href: '/trackers/trains',
-		external: false
-	},
-	{
-		name: 'planes',
-		subtitle: 'a plane pokedex: airliners, helicopters, bizjets, light aircraft and warbirds',
-		href: '/trackers/planes',
-		external: false
-	},
-	{
-		name: 'wildlife',
-		subtitle:
-			'a wild animal pokedex: everything you can spot in the Netherlands, plus famous animals worldwide',
-		href: '/trackers/wildlife',
-		external: false
-	}
 ];
+
+const strip = ({ name, subtitle, href, external, children }: Tracker): Tracker =>
+	children ? { name, subtitle, href, external, children } : { name, subtitle, href, external };
 /** Public trackers (sitemap, logged-out navigation). */
 export const trackers: readonly Tracker[] = allTrackers.filter((t) => !t.private).map(strip);
 /** Owner-only trackers. */