Add initlal service-worker with basic offline handling. Manifest is not yet present.

src/lib/components/ui/station-board/StaffServicesTable.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
 	import type { ApiStationsBoard } from '@owlboard/owlboard-ts';
-    import { formatUkTime, estClass, calculateDelay } from '$lib/utils/time';
+	import { formatUkTime, estClass, delayClassFromTimePair } from '$lib/utils/time';
 
 	let { services }: { services: ApiStationsBoard.BoardService[] } = $props();
 
@@ -8,14 +8,30 @@
 		`${s.r}${s.sta ?? ''}${s.std ?? ''}${s.wtp ?? ''}`;
 </script>
 
-<div class="table-container">
 <table class="departure-board">
+	<colgroup>
+		<col style="width:10%;" />
+		<!-- ID (Headcode) -->
+		<col style="width:17%;" />
+		<!-- ORIG (Origin) -->
+		<col style="width:17%;" />
+		<!-- DEST (Destination) -->
+		<col style="width:9%;" />
+		<!-- PLT (Platform) -->
+		<col style="width: 12%;" />
+		<!-- STA -->
+		<col style="width: 12%;" />
+		<!-- ETA/ATA -->
+		<col style="width: 12%;" />
+		<!-- STD -->
+		<col style="width: 11%;" />
+		<!-- ETD/ATD -->
+	</colgroup>
 	<thead>
 		<tr>
 			<th colspan="4" aria-hidden="true"></th>
 			<th scope="colgroup" colspan="2" class="upper-head"><abbr title="Arrival">Arr</abbr></th>
 			<th scope="colgroup" colspan="2" class="upper-head"><abbr title="Departure">Dep</abbr></th>
-                <th aria-hidden="true"></th>
 		</tr>
 		<tr>
 			<th scope="col"><abbr title="Headcode">ID</abbr></th>
@@ -26,92 +42,377 @@
 			<th scope="col"><abbr title="Actual/Expected">Act</abbr></th>
 			<th scope="col"><abbr title="Scheduled">Sch</abbr></th>
 			<th scope="col"><abbr title="Actual/Expected">Act</abbr></th>
-                <th scope="col"><abbr title="+/- Time">+/-</abbr></th>
 		</tr>
 	</thead>
 
 	{#each services as service (getRowKey(service))}
 		<tbody>
-                <tr class="service-row" class:serviceCancelled={service.c}>
+			<tr
+				class="service-row"
+				class:serviceCancelled={service.c}
+				class:servicePass={service.wtp}
+				class:serviceNonPassenger={!service.ip}
+			>
 				<td class="id-cell">{service.h}</td>
-                    <td class="orig-cell">{service.og.t}</td>
-                    <td class="dest-cell">{service.dt.t}</td>
-                    <td class="plt-cell" class:platSup={service.ps} class:platChange={service.pc}>{service.p}</td>
+				<td class="orig-cell"
+					><abbr title={service.og.n.toLocaleUpperCase()}>{service.og.t}</abbr></td
+				>
+				<td class="dest-cell"
+					><abbr title={service.dt.n.toLocaleUpperCase()}>{service.dt.t}</abbr></td
+				>
+				<td class="plt-cell" class:platSup={service.ps} class:platChange={service.pc}
+					>{service.p || '-'}</td
+				>
 
 				<!-- Handle different display for a passing train -->
 				{#if service.wtp}
-                      <td colspan="2">Pass</td>
+					<td class="pass-cell" colspan="2">Pass</td>
 					<td class="time-cell">{formatUkTime(service.wtp)}</td>
-                      <td class="time-cell {estClass(service.atp, service.etp)}">{formatUkTime(service.atp || service.etp)}</td>
+					<!-- If cancelled, show '-', otherwise check for RT or show time -->
+					<td
+						class="time-cell {estClass(service.atp, service.etp)} {delayClassFromTimePair(
+							service.wtp,
+							service.atp || service.etp
+						)}"
+					>
+						<span>
+							{service.c
+								? '-'
+								: delayClassFromTimePair(service.wtp, service.atp || service.etp) === 'delay-rt'
+									? 'RT'
+									: formatUkTime(service.atp || service.etp)}
+						</span>
+					</td>
 				{:else}
 					<td class="time-cell">{formatUkTime(service.sta)}</td>
-                      <td class="time-cell {estClass(service.ata, service.eta)}">{formatUkTime(service.ata || service.eta)}</td>
-                      <td class="time-cell">{formatUkTime(service.std)}</td>
-                      <td class="time-cell {estClass(service.atd, service.etd)}">{formatUkTime(service.atd || service.etd)}</td>
-                    {/if}
 
-                        {#if service}
-                            {@const delay = calculateDelay(service)}
-							<td class="delay-cell delay-{delay.type}">{delay.val}</td>
+					<!-- Arrival Actual/Expected -->
+					<td
+						class="time-cell {estClass(service.ata, service.eta)} {delayClassFromTimePair(
+							service.sta,
+							service.ata || service.eta
+						)}"
+					>
+						<span>
+							{service.c
+								? '-'
+								: delayClassFromTimePair(service.sta, service.ata || service.eta) === 'delay-rt'
+									? 'RT'
+									: formatUkTime(service.ata || service.eta)}
+						</span>
+					</td>
+
+					<td class="time-cell">{formatUkTime(service.std)}</td>
+
+					<!-- Departure Actual/Expected -->
+					<td
+						class="time-cell {estClass(service.atd, service.etd)} {delayClassFromTimePair(
+							service.std,
+							service.atd || service.etd
+						)}"
+					>
+						<span>
+							{service.c
+								? '-'
+								: delayClassFromTimePair(service.std, service.atd || service.etd) === 'delay-rt'
+									? 'RT'
+									: formatUkTime(service.atd || service.etd)}
+						</span>
+					</td>
 				{/if}
 			</tr>
 
+			{#if service.o}
+				<tr class="toc-coach-row">
+					<td colspan="8">
+						{service.o}
+					</td>
+				</tr>
+			{/if}
 			{#if service.c && service.cr?.r}
-                <tr>
-                    <td colspan="9">{service.cr.r}</td>
+				<tr class="cancel-row">
+					<td colspan="8">
+						{service.cr.r}
+						{#if service.cr.l}
+							{service.cr.n ? 'near' : 'at'}
+							{service.cr.l}
+						{/if}
+					</td>
+				</tr>
+			{/if}
+			{#if service.dr?.r}
+				<tr class="delay-row">
+					<td colspan="9">
+						{service.dr.r}
+						{#if service.dr.l}
+							{service.dr.n ? 'near' : 'at'}
+							{service.dr.l}
+						{/if}
+					</td>
 				</tr>
 			{/if}
 		</tbody>
 	{/each}
-
 </table>
-</div>
 
 <style>
-    .table-container {
-        width: 100%;
-    }
 	.departure-board {
 		width: 100%;
-        margin: 0 auto;
-        font-family: 'URW Gothic', sans-serif;
-        font-variant-numeric: tabular-nums;
+		margin: 5px auto;
+		border-collapse: collapse;
+		table-layout: fixed;
 	}
+
+	.departure-board td {
+		font-family: 'Inconsolata Variable', monospace;
+		font-size: clamp(1rem, 0.475rem + 2.8vw, 1.35rem);
+		font-variant-ligatures: additional-ligatures;
+		overflow: hidden;
+	}
+
+	thead,
+	.cancel-row td,
+	.delay-row td {
+		letter-spacing: -0.15ch;
+	}
+
+	thead {
+		position: sticky;
+		top: 0;
+		z-index: 2;
+		background: var(--color-bg-dark);
+	}
+
+	abbr {
+		text-decoration: none;
+		border-bottom: none;
+		cursor: help;
+	}
+
+	tbody tr:first-child td {
+		border-top: 5px solid transparent;
+	}
+
+	/* Row Logic */
 	.serviceCancelled {
-        text-decoration: line-through;
+		color: rgb(255, 131, 131);
 	}
+
+	.servicePass td {
+		opacity: 0.75;
+		font-weight: 200;
+	}
+
+	.serviceNonPassenger td {
+		opacity: 0.5;
+		font-weight: 290;
+		font-style: italic;
+	}
+
+	/* Special Row Styles */
+	.cancel-row td,
+	.delay-row td {
+		font-size: 0.88rem;
+		text-align: left;
+	}
+
+	.cancel-row td[colspan],
+	.delay-row td[colspan] {
+		padding-left: 0ch;
+	}
+
+	.cancel-row td {
+		color: rgb(255, 131, 131);
+		font-weight: 400;
+	}
+
+	.delay-row td {
+		color: var(--delay-orange);
+		font-style: italic;
+	}
+	@media (min-width: 375px) {
+		.cancel-row td,
+		.delay-row td {
+			font-size: 1.08rem;
+		}
+	}
+	@media (min-width: 420px) {
+		.cancel-row td,
+		.delay-row td {
+			font-size: 1.12rem;
+		}
+	}
+	@media (min-width: 550px) {
+		.cancel-row td,
+		.delay-row td {
+			font-size: 1.18rem;
+		}
+	}
+		@media (min-width: 620px) {
+		.cancel-row td,
+		.delay-row td {
+			font-size: 1.20rem;
+		}
+	}
+
+	.toc-coach-row td {
+		font-family: 'URW Gothic', sans-serif;
+		font-size: 0.7rem;
+		padding: 0;
+		color: rgb(187, 187, 255);
+	}
+	@media(min-width: 400px) {
+		.toc-coach-row td {
+			font-size: 0.8rem;
+		}
+	}
+	@media(min-width: 550px) {
+		.toc-coach-row td {
+			font-size: 0.85rem;
+		}
+	}
+
+	/* Column Specifics */
 	.id-cell {
-        font-family:'Courier New', Courier, monospace;
-        text-align: center;
+		text-align: left;
+		font-weight: 400;
+		font-stretch: 85%;
+		filter: brightness(0.75);
 	}
-    .orig-cell, .dest-cell {
-        color: var(--location-yellow);
+	@media (min-width: 400px) {
+		.id-cell {
+			font-stretch: 90%;
+		}
+	}
+	.orig-cell,
+	.dest-cell {
+		font-stretch: 80%;
+		font-weight: 400;
 	}
 	.orig-cell {
 		text-align: left;
+		color: var(--location-yellow);
 	}
 	.dest-cell {
 		text-align: right;
+		color: var(--location-yellow);
+	}
+	@media (min-width: 350px) {
+		.orig-cell,
+		.dest-cell {
+			font-stretch: 85%;
+		}
+		@media (min-width: 400px) {
+			.orig-cell,
+			.dest-cell {
+				font-stretch: 90%;
+			}
+		}
+		@media (min-width: 490px) {
+			.orig-cell,
+			.dest-cell {
+				font-stretch: 95%;
+			}
+		}
+		@media (min-width: 520px) {
+			.orig-cell,
+			.dest-cell {
+				font-stretch: 100%;
+			}
+			.orig-cell {
+				text-align: right;
+				padding-right: 7px;
+			}
+			.dest-cell {
+				text-align: left;
+				padding-left: 7px;
+			}
+		}
+		@media (min-width: 600px) {
+			.orig-cell,
+			.dest-cell {
+				letter-spacing: 0.05ch;
+			}
+		}
 	}
 	.plt-cell {
 		text-align: center;
+		font-weight: 410;
+		font-stretch: 100%;
 	}
-    .platChange {
-        animation: 2s fast-pulse ease-in-out infinite;
+	@media (min-width: 525px) {
+		.plt-cell {
+			font-stretch: 110%;
 		}
-    .platSup {
-        filter: opacity(0.5);
 	}
+	.plt-cell.platSup {
+		font-weight: 200;
+		opacity: 0.3;
+	}
+	.plt-cell.platChange {
+		animation: fast-pulse 2s ease-out infinite;
+	}
+	.service-row.serviceCancelled .plt-cell {
+		text-decoration: line-through;
+	}
+	.pass-cell {
+		text-align: center;
+		font-stretch: 100%;
+	}
+	/* Colour orig and dest values when cancelled */
+	.service-row.serviceCancelled .orig-cell,
+	.service-row.serviceCancelled .dest-cell {
+		color: rgb(255, 131, 131);
+	}
+
 	.time-cell {
 		text-align: center;
+		font-stretch: 72%;
 	}
-    .delay-cell {
-        text-align: center;
+	@media (min-width: 350px) {
+		.time-cell {
+			font-stretch: 77%;
 		}
-    .delay-late {
-        color: var(--delay-orange);
 	}
-    .delay-early {
+	@media (min-width: 400px) {
+		.time-cell {
+			font-stretch: 82%;
+		}
+	}
+	@media (min-width: 525px) {
+		.time-cell {
+			font-stretch: 90%;
+		}
+	}
+	@media (min-width: 600px) {
+		.time-cell {
+			font-stretch: 100%;
+		}
+	}
+
+	/* RT Logic */
+	.time-cell.delay-rt span {
+		display: none;
+	}
+	.time-cell.delay-rt::after {
+		content: 'RT';
+	}
+
+	.time-cell.delay-early {
 		color: var(--early-blue);
 	}
+
+	.time-cell.delay-late {
+		color: var(--delay-orange);
+	}
+
+	/* Time Types */
+	.est {
+		font-style: italic;
+		opacity: 0.75;
+		font-weight: 200;
+	}
+	.act {
+		font-weight: 600;
+	}
 </style>

src/lib/components/ui/station-board/StationAlertCard.svelte

@@ -41,7 +41,7 @@
 
 <style>
 	.alert-card {
-		margin: 1rem 0;
+		margin: 0;
 		border-radius: 8px;
 		background: transparent;
 		position: relative;
@@ -49,6 +49,11 @@
 		margin-bottom: 0;
 		width: 95%;
 		max-width: 750px;
+		-webkit-tap-highlight-color: transparent;
+	}
+
+	.alert-card:active {
+		filter: brightness(1.2);
 	}
 
 	.trigger {
@@ -56,7 +61,7 @@
 		display: flex;
 		border-radius: 8px;
 		align-items: center;
-		padding: 0.4rem 1rem;
+		padding: 0.1rem 1.05rem;
 		background: var(--alert-orange);
 		color: white;
 		border: none;
@@ -64,13 +69,13 @@
 		text-align: left;
 		position: relative;
 		z-index: 2;
-		height: 46px;
+		height: 40px;
 		transition: all 0.65s 0.2s;
 	}
 
 	.trigger.active {
 		border-radius: 8px 8px 0 0;
-		transition: all 0.1s 0s;
+		transition: all 0.01s 0s;
 	}
 
 	.warning-icon {
@@ -105,7 +110,7 @@
 	.content {
 		padding: 1rem;
 		position: absolute;
-		top: 46px;
+		top: 40px;
 		border-radius: 0 0 8px 8px;
 		left: 0;
 		right: 0;

src/lib/global.css

@@ -129,7 +129,41 @@
 	font-style: normal;
 	font-display: swap;
 }
+
+/* Fira Code - Variable with fallback */
+@font-face {
+	font-family: 'Fira Code';
+	src: url('/type/fira-code/FiraCode-VF.woff2') format('woff2-variations');
+	font-weight: 300 700;
+	font-style: normal;
+	font-display: swap;
+}
+@font-face {
+	font-family: 'Fira Code';
+	src: url('/type/fira-code/FiraCode-Regular.woff2') format('woff2');
+	font-weight: 400;
+	font-style: normal;
+	font-display: swap;
+}
+
+/* Inconsolata Variable */
+@font-face {
+	font-family: 'Inconsolata Variable';
+	font-style: normal;
+	font-display: swap;
+	font-weight: 200 900;
+	font-stretch: 50% 200%;
+	src: url(/type/inconsolata/latin-wdth-normal.woff2) format('woff2-variations');
+	unicode-range:
+		U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329,
+		U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+
 :root {
+	/* Fixed Heights */
+	--header-height: 80px;
+	--nav-height: 60px;
+
 	/* Brand Colours */
 	--color-brand: #4fd1d1;
 	--color-accent: #3c6f79;
@@ -159,7 +193,7 @@
 		opacity: 1;
 	}
 	50% {
-		opacity: 0.3;
+		opacity: 0.5;
 	}
 }
 

src/lib/utils/time.ts

@@ -1,6 +1,6 @@
 import type { ApiTrainsTrainDetails } from '@owlboard/owlboard-ts';
 
-export const estClass = (act: any, est: any) => (!act && est ? 'est' : 'act');
+export const estClass = (act: any, est: any) => (act ? 'act' : 'est');
 
 /**
  * Converts ISO/JSON time to UK-formatted HH:MM string, with optional (default off) seconds
@@ -10,10 +10,10 @@ export function formatUkTime(
 	dateStr: string | Date | undefined,
 	includeSeconds: boolean = false
 ): string {
-	if (!dateStr) return '--:--';
+	if (!dateStr) return '-';
 	const date = typeof dateStr === 'string' ? new Date(dateStr) : dateStr;
 
-	if (isNaN(date.getTime())) return '--:--';
+	if (isNaN(date.getTime())) return '-';
 
 	return date.toLocaleTimeString('en-GB', {
 		hour: '2-digit',
@@ -57,14 +57,20 @@ export function formatUkDateTime(
  */
 interface DelayInput {
 	// Board types
-    sta?: string | null; std?: string | null; 
-    eta?: string | null; etd?: string | null;
-    ata?: string | null; atd?: string | null;
+	sta?: string | null;
+	std?: string | null;
+	eta?: string | null;
+	etd?: string | null;
+	ata?: string | null;
+	atd?: string | null;
 
 	// Journey types
-    pta?: string | null; ptd?: string | null; 
-    wta?: string | null; wtd?: string | null;
-    atp?: string | null; wtp?: string | null;
+	pta?: string | null;
+	ptd?: string | null;
+	wta?: string | null;
+	wtd?: string | null;
+	atp?: string | null;
+	wtp?: string | null;
 	etp?: string | null;
 }
 
@@ -102,3 +108,27 @@ export function calculateDelay(loc: DelayInput): {
 		return { val: `${absDiff}E`, type: 'early' };
 	}
 }
+
+/**
+ * Accepts a pair of times (string or Date) and outputs a delay class 'delay-early', 'delay-late' or 'delay-rt'
+ * @param sched Scheduled Time (string, Date)
+ * @param act Actual Time (string, Date)
+ */
+export function delayClassFromTimePair(sched: any, act: any): string {
+	if (!sched || !act) return '';
+
+	const s = new Date(sched).getTime();
+	const a = new Date(act).getTime();
+
+	if (isNaN(s) || isNaN(a)) return '';
+
+	const diff = a - s;
+	const oneMinute = 60000;
+
+	// on-time if within one minute
+	if (Math.abs(diff) < oneMinute) {
+		return 'delay-rt';
+	}
+
+	return diff > 0 ? 'delay-late' : 'delay-early';
+}

src/routes/+error.svelte

@@ -29,7 +29,7 @@
 		</div>
 	{/if}
 
-	{#if $page.error?.owlCode === 'NETWORK_DISCONNECTED'}
+	{#if page.error?.owlCode === 'NETWORK_DISCONNECTED'}
 		<Button onclick={() => window.location.reload()} color={'accent'}>Retry</Button>
 	{:else}
 		<Button href={'/'} color={'accent'}>Return to Home</Button>

src/routes/+layout.svelte

@@ -2,9 +2,9 @@
 	import { page } from '$app/state';
 	import { slide, fade } from 'svelte/transition';
 	import { onMount } from 'svelte';
+	import { browser } from '$app/environment';
 	import { navigating } from '$app/state';
 	import { LOCATIONS } from '$lib/locations-object.svelte';
-	import { nearestStationsState } from '$lib/geohash.svelte';
 
 	import Loading from '$lib/components/ui/Loading.svelte';
 	import TimezoneWarning from '$lib/components/ui/TimezoneWarning.svelte';
@@ -17,7 +17,19 @@
 
 	import { IconHome, IconDialpad, IconSettings, IconHelp, IconDots } from '@tabler/icons-svelte';
 
-	onMount(() => LOCATIONS.init());
+	onMount(async () => {
+		LOCATIONS.init();
+		if (browser && 'serviceWorker' in navigator) {
+			try {
+				const registration = await navigator.serviceWorker.register('/service-worker.js', {
+					type: 'module',
+				});
+				console.info('OwlBoard Service Worker registered', registration.scope);
+			} catch (error) {
+				console.error('Service Worker installation failed: ', error)
+			}
+		}
+	});
 
 	let { children } = $props();
 
@@ -147,14 +159,14 @@
 	<h1 class="viewport-guard-title">Narrow Gauge Detected</h1>
 	<p>
 		Just as trains need the right track width, our data needs a bit more room to stay on the rails.
-		Please expand your view to at least 300px to view the app.
+		Please expand your view to at least 320px to view the app.
 	</p>
 </div>
 
 <style>
 	header {
 		top: 0;
-		height: 80px;
+		height: var(--header-height);
 		box-shadow: var(--shadow-std);
 	}
 	.logo-link {
@@ -201,13 +213,12 @@
 		min-height: 100dvh;
 		box-sizing: border-box;
 		background-color: var(--color-bg-dark);
-		background-image: radial-gradient(var(--color-bg-dark), var(--color-bg-light));
 	}
 
 	nav {
 		display: flex;
 		bottom: 0;
-		height: 60px;
+		height: var(--nav-height);
 		box-shadow: var(--shadow-up);
 	}
 
@@ -320,7 +331,7 @@
 		display: none;
 	}
 
-	@media (max-width: 299px) {
+	@media (max-width: 319px) {
 		.viewport-guard {
 			display: block;
 			position: fixed;

src/routes/board/+page.svelte

@@ -36,26 +36,29 @@
 </script>
 
 <section class="board-wrapper">
-	{#if data.boardData.data.m?.length}
-		<StationAlertCard messages={data.boardData.data.m} />
-	{/if}
 	<div class="time-data">
 		<span class="time-loaded">Updated: {formatUkDateTime(data.boardData.producedAt, true)}</span>
 		<span class="time-now">{formatUkTime(now, true)}</span>
 	</div>
-	{#if data.boardData.data.s?.length}
-	<StaffServicesTable services={data.boardData.data.s} />
+	{#if data.boardData.data.m?.length}
+		<StationAlertCard messages={data.boardData.data.m} />
+	{/if}
+	{#if data.boardData.data.s?.length}
+		<div class="service-list-wrapper">
+			<StaffServicesTable services={data.boardData.data.s} />
+		</div>
 	{/if}
-	<pre class="json-dump">{JSON.stringify(data.boardData.data.s, null, 2)}</pre>
 </section>
 
 <style>
 	.board-wrapper {
 		display: flex;
+		height: calc(100dvh - var(--nav-height) - var(--header-height));
 		flex-direction: column;
 		align-items: center;
 		width: 100%;
 		margin: 0 auto;
+		overflow: hidden;
 		gap: 0;
 	}
 
@@ -82,21 +85,13 @@
 		font-weight: 600;
 		font-size: 1rem;
 	}
-	pre {
-		max-width: 100%;
-		white-space: pre-wrap;
-		word-wrap: break-word;
-		box-sizing: border-box;
-		overflow-x: auto;
-	}
-	.json-dump {
-		background: #222;
-		color: #0f0;
-		padding: 1rem;
-		border-radius: 4px;
-		font-size: 0.9rem;
-		max-height: 500px;
-		width: 95%;
-		margin: 1rem auto;
+
+	.service-list-wrapper {
+		flex: 1;
+		overflow-y: auto;
+		height: calc(100dvh - 60px);
+		width: 97%;
+		max-width: 700px;
+		margin-bottom: 5px;
 	}
 </style>

src/service-worker.ts

@@ -0,0 +1,76 @@
+/// <reference types="@sveltejs/kit" />
+/// <reference lib="webworker" />
+
+import type { ApiEnvelope } from '@owlboard/api-schema-types';
+import { build, files, version } from '$service-worker';
+
+const sw = self as unknown as ServiceWorkerGlobalScope;
+const CACHE_NAME = `owlboard-cache-${version}`;
+const ASSETS = [...build, ...files, '/'];
+
+sw.addEventListener('install', (event) => {
+    event.waitUntil(
+        caches.open(CACHE_NAME).then((cache) => cache.addAll(ASSETS))
+    );
+});
+
+sw.addEventListener('activate', (event) => {
+    event.waitUntil(
+        caches.keys().then((keys) => {
+            return Promise.all(
+                keys.filter((key) => key !== CACHE_NAME).map((key) => caches.delete(key))
+            );
+        })
+    );
+});
+
+sw.addEventListener('fetch', (event) => {
+    const { request } = event;
+    if (request.method !== 'GET') return;
+    
+    const url = new URL(request.url);
+
+    // 1. Static Assets (Cache-First)
+    if (ASSETS.includes(url.pathname) || url.pathname.startsWith('/_app/')) {
+        event.respondWith(
+            caches.match(request).then((res) => res || fetch(request))
+        );
+        return;
+    }
+
+    // 2. Offline API Fallback (Network-First)
+    if (url.pathname.startsWith('/api') || url.hostname.includes('api')) {
+        event.respondWith(
+            fetch(request).catch(() => {
+                const errorObject: ApiEnvelope.Envelope = {
+                    e: {
+                        code: "NETWORK_DISCONNECTED",
+                        msg: "Cannot connect to the OwlBoard server"
+                    },
+                    t: Math.floor(Date.now() / 1000)
+                };
+                return new Response(
+                    JSON.stringify(errorObject),
+                    {
+                        status: 503,
+                        headers: { 'Content-Type': 'application/json' }
+                    }
+                );
+            })
+        );
+        return;
+    }
+
+    // 3. Navigation Fallback (The Offline 404 Catch-All)
+    // This catches top-level page navigations and hard refreshes
+    if (request.mode === 'navigate' || request.headers.get('accept')?.includes('text/html')) {
+        event.respondWith(
+            fetch(request).catch(() => {
+                // The network request failed entirely (offline).
+                // Serve the cached root shell so SvelteKit can boot.
+                return caches.match('/') as Promise<Response>;
+            })
+        );
+        return;
+    }
+});