diff --git a/eslint.config.js b/eslint.config.js
index f829a37..5221736 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -36,5 +36,5 @@ export default ts.config(
 			parser: ts.parser,
 		},
 	},
-	{ ignores: ['dist/'] },
+	{ ignores: ['dist/', 'buboard-dist/'] },
 );
diff --git a/src/App.svelte b/src/App.svelte
index 1bd277e..10fa61b 100644
--- a/src/App.svelte
+++ b/src/App.svelte
@@ -43,7 +43,7 @@
 
 <div class="app" class:resizing={isResizing}>
 	{#if !interfaceHidden}
-		<Toolbar onHide={() => (interfaceHidden = true)} />
+		<Toolbar onHide={() => { interfaceHidden = true; appState.setLocked(true); }} />
 	{/if}
 	<div class="workspace">
 		<div class="canvas-container">
@@ -63,7 +63,7 @@
 	</div>
 	{#if interfaceHidden}
 		<div class="presentation-controls">
-			<button class="show-ui" onclick={() => (interfaceHidden = false)} title="Show interface">
+			<button class="show-ui" onclick={() => { interfaceHidden = false; appState.setLocked(false); }} title="Show interface">
 				<Eye size={14} />
 			</button>
 			{#each ['1', '2', '3', '4', '5', '6', '7', '8', '9'] as key (key)}
diff --git a/src/lib/Canvas.svelte b/src/lib/Canvas.svelte
index 4b7e0ba..d08868f 100644
--- a/src/lib/Canvas.svelte
+++ b/src/lib/Canvas.svelte
@@ -38,7 +38,8 @@
 
 	function handleWheel(e: WheelEvent) {
 		e.preventDefault();
-		const factor = e.deltaY > 0 ? 0.9 : 1.1;
+		const delta = e.deltaY * (e.deltaMode === 1 ? 16 : 1);
+		const factor = Math.pow(0.995, delta);
 		const rect = container.getBoundingClientRect();
 		const cx = e.clientX - rect.left;
 		const cy = e.clientY - rect.top;
@@ -47,6 +48,7 @@
 
 	function handleDrop(e: DragEvent) {
 		e.preventDefault();
+		if (state.locked) return;
 		const files = e.dataTransfer?.files;
 		if (!files || files.length === 0) return;
 
@@ -137,6 +139,14 @@
 		if (tag === 'INPUT' || tag === 'TEXTAREA') return;
 		if ((e.target as HTMLElement)?.isContentEditable) return;
 
+		if (e.key === 'Escape') {
+			state.clearSelection();
+			state.focus(null);
+			return;
+		}
+
+		if (state.locked) return;
+
 		const mod = e.metaKey || e.ctrlKey;
 		const rect = container.getBoundingClientRect();
 		const centerX = (rect.width / 2 - state.viewport.x) / state.viewport.zoom;
@@ -163,9 +173,6 @@
 			for (let i = 1; i < newIds.length; i++) {
 				state.toggleSelection(newIds[i]);
 			}
-		} else if (e.key === 'Escape') {
-			state.clearSelection();
-			state.focus(null);
 		} else if (e.key === '[' && hasSelection) {
 			e.preventDefault();
 			for (const id of state.selectedIds) {
diff --git a/src/lib/Item.svelte b/src/lib/Item.svelte
index 2aaeb28..02d0710 100644
--- a/src/lib/Item.svelte
+++ b/src/lib/Item.svelte
@@ -191,6 +191,7 @@
 		z-index: {item.zIndex};
 		cursor: {cursorStyle()};
 		--handle-scale: {handleScale()};
+		{appState.locked ? 'pointer-events: none;' : ''}
 	"
 	onmousedown={handleMouseDown}
 	ondblclick={handleDoubleClick}
diff --git a/src/lib/Palette.svelte b/src/lib/Palette.svelte
index 644a57e..a6e736b 100644
--- a/src/lib/Palette.svelte
+++ b/src/lib/Palette.svelte
@@ -2,6 +2,8 @@
 	import { Square, Type, Image, Music, Video, Globe } from 'lucide-svelte';
 	import { state } from './state.svelte';
 
+	let locked = $derived(state.locked);
+
 	let imageInput: HTMLInputElement;
 	let soundInput: HTMLInputElement;
 	let videoInput: HTMLInputElement;
@@ -172,36 +174,38 @@
 	}
 </script>
 
-<div class="palette">
-	<button onclick={addTile} title="Tile"><Square size={14} /></button>
-	<button onclick={addText} title="Text"><Type size={14} /></button>
-	<button onclick={() => imageInput.click()} title="Image"><Image size={14} /></button>
-	<button onclick={() => soundInput.click()} title="Sound"><Music size={14} /></button>
-	<button onclick={() => videoInput.click()} title="Video"><Video size={14} /></button>
-	<button onclick={addEmbed} title="Embed"><Globe size={14} /></button>
+{#if !locked}
+	<div class="palette">
+		<button onclick={addTile} title="Tile"><Square size={14} /></button>
+		<button onclick={addText} title="Text"><Type size={14} /></button>
+		<button onclick={() => imageInput.click()} title="Image"><Image size={14} /></button>
+		<button onclick={() => soundInput.click()} title="Sound"><Music size={14} /></button>
+		<button onclick={() => videoInput.click()} title="Video"><Video size={14} /></button>
+		<button onclick={addEmbed} title="Embed"><Globe size={14} /></button>
 
-	<input
-		bind:this={imageInput}
-		type="file"
-		accept="image/*"
-		onchange={handleImageChange}
-		style="display:none"
-	/>
-	<input
-		bind:this={soundInput}
-		type="file"
-		accept="audio/*"
-		onchange={handleSoundChange}
-		style="display:none"
-	/>
-	<input
-		bind:this={videoInput}
-		type="file"
-		accept="video/*"
-		onchange={handleVideoChange}
-		style="display:none"
-	/>
-</div>
+		<input
+			bind:this={imageInput}
+			type="file"
+			accept="image/*"
+			onchange={handleImageChange}
+			style="display:none"
+		/>
+		<input
+			bind:this={soundInput}
+			type="file"
+			accept="audio/*"
+			onchange={handleSoundChange}
+			style="display:none"
+		/>
+		<input
+			bind:this={videoInput}
+			type="file"
+			accept="video/*"
+			onchange={handleVideoChange}
+			style="display:none"
+		/>
+	</div>
+{/if}
 
 <style>
 	.palette {
diff --git a/src/lib/Toolbar.svelte b/src/lib/Toolbar.svelte
index c4acb19..1276843 100644
--- a/src/lib/Toolbar.svelte
+++ b/src/lib/Toolbar.svelte
@@ -1,12 +1,13 @@
 <script lang="ts">
-	import { Upload, Download, Paintbrush, Trash2, EyeOff, ZoomIn } from 'lucide-svelte';
-	import { exportBoard, importBoard } from './io';
+	import { Upload, Download, Paintbrush, Trash2, EyeOff, ZoomIn, Combine, Lock, Unlock } from 'lucide-svelte';
+	import { exportBoard, importBoard, mergeBoard } from './io';
 	import { state } from './state.svelte';
 	import Palette from './Palette.svelte';
 
 	let { onHide }: { onHide?: () => void } = $props();
 
 	let fileInput: HTMLInputElement;
+	let mergeFileInput: HTMLInputElement;
 
 	async function handleExport() {
 		const result = await exportBoard();
@@ -30,6 +31,23 @@
 		input.value = '';
 	}
 
+	function handleMergeClick() {
+		mergeFileInput.click();
+	}
+
+	async function handleMergeChange(e: Event) {
+		const input = e.target as HTMLInputElement;
+		const files = input.files;
+		if (!files || files.length === 0) return;
+		for (const file of files) {
+			const result = await mergeBoard(file);
+			if (!result.success) {
+				alert(result.error || `Merge failed for ${file.name}`);
+			}
+		}
+		input.value = '';
+	}
+
 	function handleClear() {
 		if (confirm('Clear the canvas? This cannot be undone.')) {
 			state.reset();
@@ -93,10 +111,22 @@
 			<span>{zoomPercent}%</span>
 		</button>
 	</div>
-	<button onclick={() => state.editGlobal(true)} title="Style"><Paintbrush size={14} /></button>
-	<button onclick={handleClear} title="Clear"><Trash2 size={14} /></button>
-	<button onclick={handleImportClick} title="Import"><Upload size={14} /></button>
+	<button onclick={() => state.editGlobal(true)} title="Style" disabled={state.locked}><Paintbrush size={14} /></button>
+	<button onclick={handleClear} title="Clear" disabled={state.locked}><Trash2 size={14} /></button>
+	<button onclick={handleImportClick} title="Import" disabled={state.locked}><Upload size={14} /></button>
+	<button onclick={handleMergeClick} title="Merge" disabled={state.locked}><Combine size={14} /></button>
 	<button onclick={handleExport} title="Export"><Download size={14} /></button>
+	<button
+		class:active={state.locked}
+		onclick={() => state.setLocked(!state.locked)}
+		title={state.locked ? 'Unlock' : 'Lock'}
+	>
+		{#if state.locked}
+			<Unlock size={14} />
+		{:else}
+			<Lock size={14} />
+		{/if}
+	</button>
 	{#if onHide}
 		<button onclick={onHide} title="Hide interface"><EyeOff size={14} /></button>
 	{/if}
@@ -107,6 +137,14 @@
 		onchange={handleFileChange}
 		style="display: none"
 	/>
+	<input
+		bind:this={mergeFileInput}
+		type="file"
+		accept=".bub"
+		multiple
+		onchange={handleMergeChange}
+		style="display: none"
+	/>
 </div>
 
 <style>
@@ -163,6 +201,21 @@
 		color: var(--text, #fff);
 	}
 
+	button.active {
+		background: var(--accent, #4a9eff);
+		color: var(--text, #fff);
+	}
+
+	button:disabled {
+		opacity: 0.4;
+		cursor: not-allowed;
+	}
+
+	button:disabled:hover {
+		background: var(--surface, #282c34);
+		color: var(--text-dim, #666);
+	}
+
 	.zoom {
 		display: flex;
 		align-items: center;
diff --git a/src/lib/io.ts b/src/lib/io.ts
index 310e490..0853e49 100644
--- a/src/lib/io.ts
+++ b/src/lib/io.ts
@@ -1,5 +1,5 @@
 import JSZip from 'jszip';
-import type { Manifest, AssetStore } from './types';
+import type { Manifest, AssetStore, Item } from './types';
 import { state } from './state.svelte';
 
 export async function exportBoard(): Promise<{
@@ -110,3 +110,78 @@ export async function importBoard(
 		};
 	}
 }
+
+export async function mergeBoard(
+	file: File,
+): Promise<{ success: boolean; error?: string; itemCount?: number }> {
+	try {
+		const zip = await JSZip.loadAsync(file);
+
+		const manifestFile = zip.file('manifest.json');
+		if (!manifestFile)
+			throw new Error('Invalid .bub file: missing manifest.json');
+
+		const manifestJson = await manifestFile.async('string');
+		const raw = JSON.parse(manifestJson);
+
+		if (raw.version !== 1)
+			throw new Error(`Unsupported manifest version: ${raw.version}`);
+
+		const incomingItems: Item[] = raw.items;
+		if (incomingItems.length === 0) {
+			return { success: true, itemCount: 0 };
+		}
+
+		const assetIdMap = new Map<string, string>();
+		const newAssets: AssetStore = {};
+
+		for (const item of incomingItems) {
+			if (item.assetId && !assetIdMap.has(item.assetId)) {
+				const newAssetId = crypto.randomUUID();
+				assetIdMap.set(item.assetId, newAssetId);
+
+				const assetFiles = zip
+					.folder('assets')
+					?.file(new RegExp(`^${item.assetId}\\.`));
+				if (assetFiles && assetFiles.length > 0) {
+					const assetFile = assetFiles[0];
+					const blob = await assetFile.async('blob');
+					const url = URL.createObjectURL(blob);
+					const filename = assetFile.name.split('/').pop() || 'asset';
+					newAssets[newAssetId] = { blob, url, filename };
+				}
+			}
+		}
+
+		const minZIndex = Math.min(...incomingItems.map((i) => i.zIndex));
+		const zIndexOffset = state.maxZIndex + 1 - minZIndex;
+
+		const newItems: Item[] = incomingItems.map((item) => {
+			const newId = crypto.randomUUID();
+			const newAssetId = item.assetId ? assetIdMap.get(item.assetId) : undefined;
+
+			let html = item.html;
+			if (newAssetId && newAssets[newAssetId]) {
+				html = html.replace(/src="[^"]*"/g, `src="${newAssets[newAssetId].url}"`);
+			}
+
+			return {
+				...item,
+				id: newId,
+				assetId: newAssetId,
+				zIndex: item.zIndex + zIndexOffset,
+				html,
+			};
+		});
+
+		state.addAssets(newAssets);
+		state.addItems(newItems);
+
+		return { success: true, itemCount: newItems.length };
+	} catch (e) {
+		return {
+			success: false,
+			error: e instanceof Error ? e.message : 'Merge failed',
+		};
+	}
+}
diff --git a/src/lib/state.svelte.ts b/src/lib/state.svelte.ts
index e190574..ba41daa 100644
--- a/src/lib/state.svelte.ts
+++ b/src/lib/state.svelte.ts
@@ -73,11 +73,13 @@ function createState() {
 	});
 	let assets = $state<AssetStore>({});
 	let viewport = $state<Viewport>({ x: 0, y: 0, zoom: 1 });
-	let selectedIds = new SvelteSet<string>();
+	// eslint-disable-next-line svelte/no-unnecessary-state-wrap
+	let selectedIds = $state(new SvelteSet<string>());
 	let editingId = $state<string | null>(null);
 	let editingGlobal = $state<boolean>(false);
 	let focusedId = $state<string | null>(null);
 	let clipboard = $state<Omit<Item, 'id'>[]>([]);
+	let locked = $state<boolean>(false);
 
 	let saveTimeout: ReturnType<typeof setTimeout> | null = null;
 	let animationId: number | null = null;
@@ -166,6 +168,16 @@ function createState() {
 		save();
 	}
 
+	function addItems(items: Item[]) {
+		manifest.items.push(...items);
+		save();
+	}
+
+	function addAssets(newAssets: AssetStore) {
+		Object.assign(assets, newAssets);
+		save();
+	}
+
 	function getItem(id: string): Item | undefined {
 		return manifest.items.find((i) => i.id === id);
 	}
@@ -198,6 +210,16 @@ function createState() {
 		if (editing) editingId = null;
 	}
 
+	function setLocked(value: boolean) {
+		locked = value;
+		if (value) {
+			clearSelection();
+			focus(null);
+			edit(null);
+			editGlobal(false);
+		}
+	}
+
 	function focus(id: string | null) {
 		focusedId = id;
 	}
@@ -420,19 +442,25 @@ function createState() {
 		get focusedId() {
 			return focusedId;
 		},
+		get locked() {
+			return locked;
+		},
 		get maxZIndex() {
 			return maxZIndex;
 		},
 		addItem,
+		addItems,
 		updateItem,
 		removeItem,
 		addAsset,
+		addAssets,
 		getItem,
 		select,
 		toggleSelection,
 		clearSelection,
 		edit,
 		editGlobal,
+		setLocked,
 		focus,
 		updateSharedCss,
 		updateAppCss,