feat(hikes): medium hero variant + Switzerland-framed overview, drop static→live wobble

Three related improvements to the pre-rendered hero map system:

* New medium viewport variant (561–899 CSS px) for the per-hike detail
  hero and the /hikes overview. Tablet/split-pane viewports were
  getting the wide pose (chosen for ~1920 CSS px), which landed too
  zoomed in. Each variant is rendered at a pose matching its
  container, so the static→Leaflet handover aligns at every band.
  Manifest fields are optional — pages fall back to the wide variant
  on tablets until build-hikes regenerates the images.

* Overview frames on Switzerland (fixed center [46.82, 8.23]) with
  explicit per-variant zooms (wide=8, medium=8, narrow=7) rather than
  auto-fitting the union of hike bboxes. The previous behavior zoomed
  in on whichever corner the catalogue clustered in; this reads as
  "hikes across CH". Bumps OVERVIEW_RENDER_VERSION so cached overview
  images get invalidated on the next build.

* Removed the post-tile-load flyToBounds in both HikeMap.svelte and
  HikesOverviewMap.svelte. The map already opens at the static pose
  via setView; the second auto-fit was adding a visible wobble on
  routes whose bbox sits at an integer-zoom boundary (e.g. the
  Einsiedeln–Unteriberg detail), where the build-time fit and
  Leaflet's runtime fit disagree by one zoom step at the user's
  actual container size.

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "homepage",
-	"version": "1.90.0",
+	"version": "1.91.0",
 	"private": true,
 	"type": "module",
 	"scripts": {

scripts/build-hikes.ts

@@ -29,7 +29,7 @@ import {
 	type GpxStage
 } from '../src/lib/server/gpx.js';
 import { simplifyTrack } from '../src/lib/server/simplifyTrack.js';
-import { computeStaticMapPose, renderOverviewMap, renderStaticMap } from './staticHikeMap.js';
+import { computeStaticMapPose, lngLatToPx, renderOverviewMap, renderStaticMap } from './staticHikeMap.js';
 import { sacTrailColor, SAC_TRAIL_COLOR } from '../src/lib/data/sacColors.js';
 import { computeElevationStats, computeElevationRange } from '../src/lib/hikes/elevation.js';
 import type {
@@ -692,7 +692,17 @@ const HERO_NARROW_HEIGHT = 1200;
 const HERO_NARROW_FIT_WIDTH = 400;
 const HERO_NARROW_FIT_HEIGHT = 480;
 
-type HeroVariant = 'wide' | 'narrow';
+// Medium-viewport variant for the 561–899 px CSS width band (tablets, split
+// panes, small laptops). Picks an in-between pose so the auto-fit zoom
+// matches what Leaflet computes at tablet widths — without this the wide
+// hero (chosen for ~1920 CSS px) lands too zoomed-in on tablets, and the
+// narrow hero (chosen for ~400 CSS px) lands too zoomed-out.
+const HERO_MEDIUM_WIDTH = 2400;
+const HERO_MEDIUM_HEIGHT = 1500;
+const HERO_MEDIUM_FIT_WIDTH = 1000;
+const HERO_MEDIUM_FIT_HEIGHT = 500;
+
+type HeroVariant = 'wide' | 'medium' | 'narrow';
 
 const HERO_VARIANT_SPECS: ReadonlyArray<{
 	name: HeroVariant;
@@ -708,6 +718,13 @@ const HERO_VARIANT_SPECS: ReadonlyArray<{
 		fitWidth: HERO_FIT_WIDTH,
 		fitHeight: HERO_FIT_HEIGHT
 	},
+	{
+		name: 'medium',
+		width: HERO_MEDIUM_WIDTH,
+		height: HERO_MEDIUM_HEIGHT,
+		fitWidth: HERO_MEDIUM_FIT_WIDTH,
+		fitHeight: HERO_MEDIUM_FIT_HEIGHT
+	},
 	{
 		name: 'narrow',
 		width: HERO_NARROW_WIDTH,
@@ -717,32 +734,23 @@ const HERO_VARIANT_SPECS: ReadonlyArray<{
 	}
 ];
 
-// Padding + max-zoom match the live overview map's
+// Bump when the overview renderer's output changes — e.g. stroke widths,
-// `fitBounds(..., { padding: [32, 32], maxZoom: 13 })` so the static lands
+// palette tweaks, framing constants in `processOverview`.
-// at the same pose Leaflet will fit to. fitHeight matches the page's
+const OVERVIEW_RENDER_VERSION = 2;
-// `clamp(320px, 50vh, 520px)` hero at desktop viewports.
-const OVERVIEW_FIT_WIDTH = 1920;
-const OVERVIEW_FIT_HEIGHT = 520;
-const OVERVIEW_PADDING_PX = 32;
-const OVERVIEW_MAX_ZOOM = 13;
-// Bump alongside `HERO_RENDER_VERSION` (or independently) when the overview
-// renderer's output changes — e.g. stroke widths, palette tweaks.
-const OVERVIEW_RENDER_VERSION = 1;
 
 type OverviewVariantSpec = {
 	name: HeroVariant;
 	width: number;
 	height: number;
-	fitWidth: number;
-	fitHeight: number;
 };
 
-// Overview narrow uses the same canvas dims as the per-hike narrow but
+// One spec per viewport band; the overview's per-variant zoom is fixed in
-// fits the union bbox at phone size — same `maxZoom: 13` clamp as the
+// `processOverview` rather than being derived from a fit bbox, so we only
-// live map's `fitBounds`.
+// need to know the output canvas size here.
 const OVERVIEW_VARIANT_SPECS: ReadonlyArray<OverviewVariantSpec> = [
-	{ name: 'wide', width: HERO_WIDTH, height: HERO_HEIGHT, fitWidth: OVERVIEW_FIT_WIDTH, fitHeight: OVERVIEW_FIT_HEIGHT },
+	{ name: 'wide', width: HERO_WIDTH, height: HERO_HEIGHT },
-	{ name: 'narrow', width: HERO_NARROW_WIDTH, height: HERO_NARROW_HEIGHT, fitWidth: HERO_NARROW_FIT_WIDTH, fitHeight: HERO_NARROW_FIT_HEIGHT }
+	{ name: 'medium', width: HERO_MEDIUM_WIDTH, height: HERO_MEDIUM_HEIGHT },
+	{ name: 'narrow', width: HERO_NARROW_WIDTH, height: HERO_NARROW_HEIGHT }
 ];
 
 type OverviewVariantResult = {
@@ -764,49 +772,47 @@ async function processOverview(
 		}));
 	if (lines.length === 0) return undefined;
 
-	// Union bbox over every hike's bbox — that's what Leaflet's
+	// Frame on Switzerland, not the union of hike bboxes — the overview
-	// `fitBounds(bounds)` operates on with `extend()` per polyline. Using
+	// reads as "hikes across CH" instead of zooming in on whichever corner
-	// each hike's bbox rather than every polyline point keeps the math
+	// the catalogue clusters in. Center is the country's approximate
-	// cheap without losing the framing accuracy.
+	// geographic midpoint; zoom is picked per-variant so CH fills the
-	let minLat = Infinity, maxLat = -Infinity, minLng = Infinity, maxLng = -Infinity;
+	// hero at each viewport without the country bbox having to fit
-	for (const h of hikes) {
+	// pixel-perfectly inside `OVERVIEW_FIT_*` (which would force the wide
-		const [a, b, c, d] = h.bbox;
+	// variant down to z=7 — too far out). At these zooms the rendered
-		if (a < minLat) minLat = a;
+	// canvas slightly overflows the visible hero on the short axis, and
-		if (c > maxLat) maxLat = c;
+	// `object-fit: none` crops to the centre — exactly what we want for
-		if (b < minLng) minLng = b;
+	// a "frame on the country" composition.
-		if (d > maxLng) maxLng = d;
+	const CH_CENTER: [number, number] = [46.82, 8.23];
-	}
+	const OVERVIEW_ZOOM_BY_VARIANT: Record<HeroVariant, number> = {
-	if (!Number.isFinite(minLat)) return undefined;
+		wide: 8,
-	const bbox: [number, number, number, number] = [minLat, minLng, maxLat, maxLng];
+		medium: 8,
+		narrow: 7
+	};
 
 	const slug = '_overview';
 	const outDir = path.join(HIKES_ASSETS_DIR, slug, 'images');
 	await fs.mkdir(outDir, { recursive: true });
 
 	async function renderVariant(spec: OverviewVariantSpec): Promise<OverviewVariantResult | undefined> {
-		const pose = computeStaticMapPose({
+		const zoom = OVERVIEW_ZOOM_BY_VARIANT[spec.name];
-			bbox,
+		const c = lngLatToPx(CH_CENTER[1], CH_CENTER[0], zoom);
-			width: spec.width,
+		const pose = {
-			height: spec.height,
+			zoom,
-			paddingPx: OVERVIEW_PADDING_PX,
+			centerLat: CH_CENTER[0],
-			fitWidth: spec.fitWidth,
+			centerLng: CH_CENTER[1],
-			fitHeight: spec.fitHeight,
+			originX: Math.round(c.x - spec.width / 2),
-			maxZoom: OVERVIEW_MAX_ZOOM
+			originY: Math.round(c.y - spec.height / 2)
-		});
+		};
-		if (!pose) return undefined;
 
 		const hash = crypto
 			.createHash('sha256')
 			.update(
 				JSON.stringify({
-					bbox,
+					center: CH_CENTER,
+					zoom,
 					w: spec.width,
 					h: spec.height,
-					fw: spec.fitWidth,
-					fh: spec.fitHeight,
 					lines,
-					maxZoom: OVERVIEW_MAX_ZOOM,
-					pad: OVERVIEW_PADDING_PX,
 					v: OVERVIEW_RENDER_VERSION
 				})
 			)
@@ -877,6 +883,9 @@ async function processOverview(
 		url: byVariant.wide.url,
 		zoom: byVariant.wide.zoom,
 		center: byVariant.wide.center,
+		urlMedium: byVariant.medium?.url,
+		zoomMedium: byVariant.medium?.zoom,
+		centerMedium: byVariant.medium?.center,
 		urlNarrow: byVariant.narrow?.url,
 		zoomNarrow: byVariant.narrow?.zoom,
 		centerNarrow: byVariant.narrow?.center
@@ -1388,11 +1397,16 @@ async function buildHike(slug: string, cache: GeocodeCache): Promise<HikeManifes
 
 	const iconUrl = iconResult?.url;
 	const heroWide = heroResult?.wide;
+	const heroMedium = heroResult?.medium;
 	const heroNarrow = heroResult?.narrow;
 	const heroMapUrlLight = heroWide?.lightUrl;
 	const heroMapUrlDark = heroWide?.darkUrl;
 	const heroMapZoom = heroWide?.zoom;
 	const heroMapCenter = heroWide?.center;
+	const heroMapUrlLightMedium = heroMedium?.lightUrl;
+	const heroMapUrlDarkMedium = heroMedium?.darkUrl;
+	const heroMapZoomMedium = heroMedium?.zoom;
+	const heroMapCenterMedium = heroMedium?.center;
 	const heroMapUrlLightNarrow = heroNarrow?.lightUrl;
 	const heroMapUrlDarkNarrow = heroNarrow?.darkUrl;
 	const heroMapZoomNarrow = heroNarrow?.zoom;
@@ -1431,6 +1445,10 @@ async function buildHike(slug: string, cache: GeocodeCache): Promise<HikeManifes
 		heroMapUrlDark,
 		heroMapZoom,
 		heroMapCenter,
+		heroMapUrlLightMedium,
+		heroMapUrlDarkMedium,
+		heroMapZoomMedium,
+		heroMapCenterMedium,
 		heroMapUrlLightNarrow,
 		heroMapUrlDarkNarrow,
 		heroMapZoomNarrow,

scripts/staticHikeMap.ts

@@ -30,7 +30,7 @@ function tileUrl(sub: string, layer: string, z: number, x: number, y: number): s
 }
 
 /** Web Mercator: lng/lat → absolute pixel coordinate at a given zoom. */
-function lngLatToPx(lng: number, lat: number, zoom: number): { x: number; y: number } {
+export function lngLatToPx(lng: number, lat: number, zoom: number): { x: number; y: number } {
 	const n = 2 ** zoom;
 	const x = ((lng + 180) / 360) * n * TILE_SIZE;
 	const latRad = (lat * Math.PI) / 180;

src/lib/components/hikes/HikeMap.svelte

@@ -191,50 +191,17 @@
 			let currentBase: BaseLayer = 'schematic';
 
 			// First-paint handover: when the schematic tile layer finishes
-			// loading its initial batch, fire `onReady` (so the static hero
+			// loading its initial batch, fire `onReady` so the static hero
-			// can fade out) AND — if we opened with `setView` to match a
+			// can fade out. The map already opened at the static pose via
-			// pre-rendered hero — animate to Leaflet's natural `fitBounds`
+			// `setView(initialCenter, initialZoom)` below, so the live
-			// view, which is typically slightly more zoomed out. The fade
+			// tiles paint over the static at the same framing — no second
-			// (~450 ms) overlaps with the zoom animation (~700 ms) so the
+			// animation is needed (and a `flyToBounds` here would actually
-			// user sees the map ease into its proper framing as the static
+			// cause a visible wobble on hikes whose bbox sits right at an
-			// dissolves.
+			// integer-zoom boundary, where the static's fit and Leaflet's
+			// runtime fit disagree by one zoom step at the user's actual
+			// container size).
 			tileLayers.schematic.once('load', () => {
-				// Initial tiles at the static-hero pose are present. If we
-				// don't need to fly to a different framing, fire `onReady`
-				// straight away — that's the simple path.
-				if (!initialCenter || typeof initialZoom !== 'number') {
 				onReady?.();
-					return;
-				}
-
-				// Otherwise: start the fly-to-bounds animation while the
-				// static stays visible on top. Once the fly settles AND the
-				// new tiles for the final view are in (or a short safety
-				// window elapses), THEN fire `onReady` so the static fades
-				// out over fully-loaded tiles — no grey flash in the gap
-				// between fly-end and tile-load.
-				map.flyToBounds(initialBounds, {
-					padding: [24, 24],
-					duration: 0.9,
-					easeLinearity: 0.3
-				});
-				map.once('moveend', () => {
-					let fired = false;
-					const fire = () => {
-						if (fired) return;
-						fired = true;
-						onReady?.();
-					};
-					// `load` fires when every currently-visible tile has
-					// arrived. Usually that's the trigger.
-					tileLayers.schematic.once('load', fire);
-					// Safety net: if the fly didn't change zoom enough to
-					// require any new tiles, `load` may not re-fire. 350 ms
-					// is short enough to feel responsive, long enough for
-					// the post-fly tile batch to arrive on typical
-					// connections.
-					setTimeout(fire, 350);
-				});
 			});
 
 			// Canvas-rendered polylines can't resolve CSS custom properties,

src/lib/components/hikes/HikesOverviewMap.svelte

@@ -151,35 +151,17 @@
 			// union bounds.
 			let initialBounds: ReturnType<typeof L.latLngBounds> | null = null;
 
-			// First-paint handover: when the schematic tile layer finishes
+			// First-paint handover: fire `onReady` once the schematic tile
-			// loading its initial batch, fire `onReady` (so the static hero
+			// layer's initial batch loads so the static hero can fade out.
-			// can fade out) and — if we opened with `setView` to match a
+			// The map already opened at the static pose via setView (see
-			// pre-rendered hero — animate to Leaflet's natural `fitBounds`
+			// the initialCenter branch below), so no extra animation is
-			// of the union polyline bounds. The fade overlaps with the zoom
+			// needed — and `flyToBounds(union)` here used to cause a
-			// animation so the user sees the map ease into its final
+			// visible wobble on hikes whose union bbox sits at an integer-
-			// framing as the static dissolves. Mirrors the same pattern in
+			// zoom boundary, where the static's fit and Leaflet's runtime
+			// fit disagree by one zoom step. Mirrors the same fix in
 			// `HikeMap.svelte`.
 			tileLayers.schematic.once('load', () => {
-				if (!initialCenter || typeof initialZoom !== 'number' || !initialBounds) {
 				onReady?.();
-					return;
-				}
-				map.flyToBounds(initialBounds, {
-					padding: [32, 32],
-					maxZoom: 13,
-					duration: 0.9,
-					easeLinearity: 0.3
-				});
-				map.once('moveend', () => {
-					let fired = false;
-					const fire = () => {
-						if (fired) return;
-						fired = true;
-						onReady?.();
-					};
-					tileLayers.schematic.once('load', fire);
-					setTimeout(fire, 350);
-				});
 			});
 
 			// One polyline per hike, sourced from the manifest's already-

src/routes/hikes/+page.svelte

@@ -28,22 +28,30 @@
 	// page's hero map.
 	let heroMapReady = $state(false);
 
-	// Phone vs. desktop viewport switch — drives which pre-rendered pose
+	// Three-band viewport switch — drives which pre-rendered pose
-	// (`HIKES_OVERVIEW.zoom/center` vs. `.zoomNarrow/.centerNarrow`) we
+	// (`HIKES_OVERVIEW.zoom/center` vs. `.zoomMedium/.centerMedium` vs.
-	// hand to Leaflet's first `setView` so it lands aligned with whichever
+	// `.zoomNarrow/.centerNarrow`) we hand to Leaflet's first `setView` so
-	// static `<img>` the CSS is showing. Starts `false` to match SSR (which
+	// it lands aligned with whichever static `<img>` the CSS is showing.
-	// has no window); the $effect snaps it to the real value on mount and
+	// Starts `false`/`false` to match SSR (which has no window); the
-	// keeps it in sync if the user rotates / resizes across the breakpoint.
+	// $effect snaps to the real value on mount and keeps both flags in
+	// sync across rotate/resize. `narrow` wins over `medium` when both
+	// would match (≤560 is also <900).
 	let narrowViewport = $state(false);
+	let mediumViewport = $state(false);
 	$effect(() => {
 		if (typeof window === 'undefined') return;
-		const mq = window.matchMedia('(max-width: 560px)');
+		const mqNarrow = window.matchMedia('(max-width: 560px)');
-		narrowViewport = mq.matches;
+		const mqMedium = window.matchMedia('(min-width: 561px) and (max-width: 899px)');
-		const onChange = (e: MediaQueryListEvent) => {
+		narrowViewport = mqNarrow.matches;
-			narrowViewport = e.matches;
+		mediumViewport = mqMedium.matches;
+		const onNarrow = (e: MediaQueryListEvent) => { narrowViewport = e.matches; };
+		const onMedium = (e: MediaQueryListEvent) => { mediumViewport = e.matches; };
+		mqNarrow.addEventListener('change', onNarrow);
+		mqMedium.addEventListener('change', onMedium);
+		return () => {
+			mqNarrow.removeEventListener('change', onNarrow);
+			mqMedium.removeEventListener('change', onMedium);
 		};
-		mq.addEventListener('change', onChange);
-		return () => mq.removeEventListener('change', onChange);
 	});
 
 	const overviewPose = $derived.by(() => {
@@ -51,6 +59,9 @@
 		if (narrowViewport && HIKES_OVERVIEW.urlNarrow && HIKES_OVERVIEW.centerNarrow && typeof HIKES_OVERVIEW.zoomNarrow === 'number') {
 			return { center: HIKES_OVERVIEW.centerNarrow, zoom: HIKES_OVERVIEW.zoomNarrow };
 		}
+		if (mediumViewport && HIKES_OVERVIEW.urlMedium && HIKES_OVERVIEW.centerMedium && typeof HIKES_OVERVIEW.zoomMedium === 'number') {
+			return { center: HIKES_OVERVIEW.centerMedium, zoom: HIKES_OVERVIEW.zoomMedium };
+		}
 		return { center: HIKES_OVERVIEW.center, zoom: HIKES_OVERVIEW.zoom };
 	});
 
@@ -193,9 +204,9 @@
 			     visible hike's preview polyline, coloured by SAC tier.
 			     Displayed at native pixel size (`object-fit: none`) so it
 			     overlays Leaflet's live tiles exactly. The image fades out
-			     once Leaflet's first tile batch loads. Two width variants
+			     once Leaflet's first tile batch loads. Three width variants
-			     ship — desktop (wide pose) and phone (narrow pose, ≤560 CSS
+			     ship — wide (≥900 CSS px), medium (561–899), narrow (≤560).
-			     px). CSS chooses which one shows based on a media query so
+			     CSS chooses which one shows based on a media query so
 			     hydration doesn't need to wait. -->
 			<img
 				class="hero-static hero-static-wide"
@@ -206,6 +217,17 @@
 				loading="eager"
 				decoding="async"
 			/>
+			{#if HIKES_OVERVIEW.urlMedium}
+				<img
+					class="hero-static hero-static-medium"
+					class:faded={heroMapReady}
+					src={HIKES_OVERVIEW.urlMedium}
+					alt=""
+					aria-hidden="true"
+					loading="eager"
+					decoding="async"
+				/>
+			{/if}
 			{#if HIKES_OVERVIEW.urlNarrow}
 				<img
 					class="hero-static hero-static-narrow"
@@ -325,13 +347,20 @@
 		opacity: 0;
 	}
 
-	/* Wide ↔ narrow viewport swap. The narrow variant is rendered at a
+	/* Three-band viewport swap (wide ≥900, medium 561–899, narrow ≤560).
-	 * phone-sized fit, so the zoom matches what Leaflet picks at the same
+	 * Each variant is rendered at a fit matching its band so Leaflet picks
-	 * container width — without this the desktop hero would land too
+	 * the same zoom on first paint — without this the desktop hero would
-	 * zoomed-in on phones (its pose was chosen for ~1920 CSS px). */
+	 * land too zoomed-in on tablets/phones (its pose was chosen for
+	 * ~1920 CSS px), and the narrow hero would land too zoomed-out on
+	 * tablets (chosen for ~400 CSS px). */
+	.hero-static-medium,
 	.hero-static-narrow { display: none; }
-	@media (max-width: 560px) {
+	@media (max-width: 899px) {
 		.hero-static-wide { display: none; }
+		.hero-static-medium { display: block; }
+	}
+	@media (max-width: 560px) {
+		.hero-static-medium { display: none; }
 		.hero-static-narrow { display: block; }
 	}
 

src/routes/hikes/[slug]/+page.svelte

@@ -40,22 +40,29 @@
 	// handover is a soft cross-fade rather than a swap.
 	let heroMapReady = $state(false);
 
-	// Phone vs. desktop viewport — picks which pre-rendered pose we hand
+	// Three-band viewport switch (narrow ≤560, medium 561–899, wide ≥900)
-	// to Leaflet's first `setView` so it lands aligned with the static
+	// — picks which pre-rendered pose we hand to Leaflet's first `setView`
-	// `<img>` the CSS is showing. Starts `false` for SSR; the $effect snaps
+	// so it lands aligned with the static `<img>` the CSS is showing.
-	// it to the real value on mount and keeps it in sync across rotate /
+	// Starts `false`/`false` for SSR; the $effect snaps to real values on
-	// resize. See `/hikes/+page.svelte` for the matching overview-side
+	// mount and keeps both flags in sync across rotate/resize. `narrow`
-	// pattern.
+	// wins over `medium` when both would match. See the matching overview
+	// pattern in `/hikes/+page.svelte`.
 	let narrowViewport = $state(false);
+	let mediumViewport = $state(false);
 	$effect(() => {
 		if (typeof window === 'undefined') return;
-		const mq = window.matchMedia('(max-width: 560px)');
+		const mqNarrow = window.matchMedia('(max-width: 560px)');
-		narrowViewport = mq.matches;
+		const mqMedium = window.matchMedia('(min-width: 561px) and (max-width: 899px)');
-		const onChange = (e: MediaQueryListEvent) => {
+		narrowViewport = mqNarrow.matches;
-			narrowViewport = e.matches;
+		mediumViewport = mqMedium.matches;
+		const onNarrow = (e: MediaQueryListEvent) => { narrowViewport = e.matches; };
+		const onMedium = (e: MediaQueryListEvent) => { mediumViewport = e.matches; };
+		mqNarrow.addEventListener('change', onNarrow);
+		mqMedium.addEventListener('change', onMedium);
+		return () => {
+			mqNarrow.removeEventListener('change', onNarrow);
+			mqMedium.removeEventListener('change', onMedium);
 		};
-		mq.addEventListener('change', onChange);
-		return () => mq.removeEventListener('change', onChange);
 	});
 
 	const canton = $derived(resolveCanton(hike.canton));
@@ -84,6 +91,13 @@
 		) {
 			return { center: hike.heroMapCenterNarrow, zoom: hike.heroMapZoomNarrow };
 		}
+		if (
+			mediumViewport &&
+			hike.heroMapCenterMedium &&
+			typeof hike.heroMapZoomMedium === 'number'
+		) {
+			return { center: hike.heroMapCenterMedium, zoom: hike.heroMapZoomMedium };
+		}
 		if (hike.heroMapCenter && typeof hike.heroMapZoom === 'number') {
 			return { center: hike.heroMapCenter, zoom: hike.heroMapZoom };
 		}
@@ -284,14 +298,14 @@
 	<section class="hero-map" style="view-transition-name: hike-{hike.slug}; view-transition-class: hike-fly-in">
 		{#if hike.heroMapUrlLight}
 			<!-- Build-time static composite of Swisstopo tiles + the trail
-			     polyline + public photo markers. Four variants ship — theme
+			     polyline + public photo markers. Six variants ship — theme
-			     (light/dark) × viewport (wide/narrow). Theme is picked by
+			     (light/dark) × viewport (wide ≥900 / medium 561–899 /
-			     `data-theme` / `prefers-color-scheme`; viewport by a
+			     narrow ≤560 CSS px). Theme is picked by `data-theme` /
-			     `max-width: 560px` media query. Each variant is rendered at
+			     `prefers-color-scheme`; viewport by media queries. Each
-			     the same pose Leaflet's `fitBounds` picks for its target
+			     variant is rendered at the same pose Leaflet's `fitBounds`
-			     container size, so the static→live cross-fade aligns
+			     picks for its target container size, so the static→live
-			     pixel-perfectly. The image fades out once Leaflet's first
+			     cross-fade aligns pixel-perfectly. The image fades out once
-			     tile batch loads. -->
+			     Leaflet's first tile batch loads. -->
 			<img
 				class="hero-static hero-static-light hero-static-wide"
 				class:faded={heroMapReady}
@@ -313,6 +327,28 @@
 				decoding="async"
 			/>
 		{/if}
+		{#if hike.heroMapUrlLightMedium}
+			<img
+				class="hero-static hero-static-light hero-static-medium"
+				class:faded={heroMapReady}
+				src={hike.heroMapUrlLightMedium}
+				alt=""
+				aria-hidden="true"
+				loading="eager"
+				decoding="async"
+			/>
+		{/if}
+		{#if hike.heroMapUrlDarkMedium}
+			<img
+				class="hero-static hero-static-dark hero-static-medium"
+				class:faded={heroMapReady}
+				src={hike.heroMapUrlDarkMedium}
+				alt=""
+				aria-hidden="true"
+				loading="eager"
+				decoding="async"
+			/>
+		{/if}
 		{#if hike.heroMapUrlLightNarrow}
 			<img
 				class="hero-static hero-static-light hero-static-narrow"
@@ -573,28 +609,37 @@
 		pointer-events: none;
 	}
 
-	/* 2×2 picker: theme (light/dark) × viewport (wide/narrow). Each `<img>`
+	/* 2×3 picker: theme (light/dark) × viewport (wide ≥900 / medium
-	 * has both qualifiers (e.g. `.hero-static-light.hero-static-wide`); we
+	 * 561–899 / narrow ≤560). Each `<img>` carries both qualifiers (e.g.
-	 * hide everything by default and reveal exactly one based on the
+	 * `.hero-static-light.hero-static-wide`); we hide everything by
-	 * active theme and the `max-width: 560px` media query. The narrow
+	 * default and reveal exactly one based on the active theme and the
-	 * variant uses a phone-sized pose so the auto-fit zoom matches what
+	 * viewport media queries. Each variant is rendered at a fit matching
-	 * Leaflet picks at the same container width. */
+	 * its band so Leaflet picks the same integer zoom on first paint. */
 	.hero-static { display: none; }
 
-	/* Default (light theme assumed, no `data-theme` attribute, no
+	/* Default (light theme assumed): show the wide-light, then step down
-	 * `prefers-color-scheme: dark`): show the wide-light variant. */
+	 * the cascade as viewports shrink. */
 	.hero-static-light.hero-static-wide { display: block; }
-	@media (max-width: 560px) {
+	@media (max-width: 899px) {
 		.hero-static-light.hero-static-wide { display: none; }
+		.hero-static-light.hero-static-medium { display: block; }
+	}
+	@media (max-width: 560px) {
+		.hero-static-light.hero-static-medium { display: none; }
 		.hero-static-light.hero-static-narrow { display: block; }
 	}
 
 	@media (prefers-color-scheme: dark) {
 		.hero-static-light.hero-static-wide,
+		.hero-static-light.hero-static-medium,
 		.hero-static-light.hero-static-narrow { display: none; }
 		.hero-static-dark.hero-static-wide { display: block; }
-		@media (max-width: 560px) {
+		@media (max-width: 899px) {
 			.hero-static-dark.hero-static-wide { display: none; }
+			.hero-static-dark.hero-static-medium { display: block; }
+		}
+		@media (max-width: 560px) {
+			.hero-static-dark.hero-static-medium { display: none; }
 			.hero-static-dark.hero-static-narrow { display: block; }
 		}
 	}
@@ -602,15 +647,23 @@
 	/* Explicit `data-theme` always wins. */
 	:global(:root[data-theme='light']) .hero-static-dark { display: none !important; }
 	:global(:root[data-theme='light']) .hero-static-light.hero-static-wide { display: block; }
-	@media (max-width: 560px) {
+	@media (max-width: 899px) {
 		:global(:root[data-theme='light']) .hero-static-light.hero-static-wide { display: none; }
+		:global(:root[data-theme='light']) .hero-static-light.hero-static-medium { display: block; }
+	}
+	@media (max-width: 560px) {
+		:global(:root[data-theme='light']) .hero-static-light.hero-static-medium { display: none; }
 		:global(:root[data-theme='light']) .hero-static-light.hero-static-narrow { display: block; }
 	}
 
 	:global(:root[data-theme='dark']) .hero-static-light { display: none !important; }
 	:global(:root[data-theme='dark']) .hero-static-dark.hero-static-wide { display: block; }
-	@media (max-width: 560px) {
+	@media (max-width: 899px) {
 		:global(:root[data-theme='dark']) .hero-static-dark.hero-static-wide { display: none; }
+		:global(:root[data-theme='dark']) .hero-static-dark.hero-static-medium { display: block; }
+	}
+	@media (max-width: 560px) {
+		:global(:root[data-theme='dark']) .hero-static-dark.hero-static-medium { display: none; }
 		:global(:root[data-theme='dark']) .hero-static-dark.hero-static-narrow { display: block; }
 	}
 

src/types/hikes.ts

@@ -129,6 +129,15 @@ export type HikeManifestEntry = {
 	/** Map centre `[lat, lng]` the static hero was rendered around. */
 	heroMapCenter?: [number, number];
 
+	/** Medium-viewport variant (561–899 CSS px — tablets, split panes,
+	 * small laptops). Pose picked for a tablet-sized container so the
+	 * static→Leaflet handover lands at the same integer zoom without the
+	 * "too zoomed in" mismatch the wide pose would produce at this width. */
+	heroMapUrlLightMedium?: string;
+	heroMapUrlDarkMedium?: string;
+	heroMapZoomMedium?: number;
+	heroMapCenterMedium?: [number, number];
+
 	/** Narrow-viewport variant of the pre-rendered hero (≤ 560 CSS px).
 	 * Rendered with a phone-sized `fitWidth`/`fitHeight`, so the chosen
 	 * integer zoom matches what Leaflet's `fitBounds` picks at the same
@@ -162,6 +171,12 @@ export type HikesOverview = {
 	zoom: number;
 	/** Centre `[lat, lng]` the wide static was rendered around. */
 	center: [number, number];
+	/** Medium-viewport variant (561–899 CSS px). Pose picked for a tablet-
+	 * sized container so the static→Leaflet handover doesn't shift the map
+	 * at this width. */
+	urlMedium?: string;
+	zoomMedium?: number;
+	centerMedium?: [number, number];
 	/** Narrow-viewport variant for phones (≤ 560 CSS px). Rendered at a
 	 * phone-sized `fitWidth`/`fitHeight`, so the chosen zoom matches what
 	 * Leaflet picks at the same container size. The page shows it instead