diff --git a/TODO.md b/TODO.md
index 33fcac3..66e92ba 100644
--- a/TODO.md
+++ b/TODO.md
@@ -188,7 +188,7 @@ Functionality:
 
 * JS
 	* Organize things into files better; "functions.js" is like ONE step above saying "code.js"
-	* `$ToolWindow` has a `$Button` facility; `$DialogWindow` overrides it with essentially a better one
+	* `$ToolWindow` has a `$Button` facility; `$DialogWindow` overrides it with essentially a better one; now there's `showMessageBox` too! and `$ToolWindow` is a wrapper for OS-GUI's `$Window`, and should be removed at some point; btw, should `show_error_message` functionality be folded into `showMessageBox`?
 	* Make code clearer / improve code quality
 		* https://codeclimate.com/github/1j01/jspaint
 
diff --git a/audio/chord.wav b/audio/chord.wav
new file mode 100644
index 0000000..0193a11
Binary files /dev/null and b/audio/chord.wav differ
diff --git a/images/error-16x16-8bpp.png b/images/error-16x16-8bpp.png
new file mode 100644
index 0000000..476549a
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diff --git a/images/error-32x32-1bpp.png b/images/error-32x32-1bpp.png
new file mode 100644
index 0000000..4d2d158
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diff --git a/images/error-32x32-8bpp.png b/images/error-32x32-8bpp.png
new file mode 100644
index 0000000..a1bdc2f
Binary files /dev/null and b/images/error-32x32-8bpp.png differ
diff --git a/images/info-16x16-8bpp.png b/images/info-16x16-8bpp.png
new file mode 100644
index 0000000..3c3fc61
Binary files /dev/null and b/images/info-16x16-8bpp.png differ
diff --git a/images/info-32x32-1bpp.png b/images/info-32x32-1bpp.png
new file mode 100644
index 0000000..5ad5680
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diff --git a/images/info-32x32-8bpp.png b/images/info-32x32-8bpp.png
new file mode 100644
index 0000000..101841f
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diff --git a/images/nuke-32x32-8bpp.png b/images/nuke-32x32-8bpp.png
new file mode 100644
index 0000000..9d6b9ba
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diff --git a/images/question-32x32-1bpp.png b/images/question-32x32-1bpp.png
new file mode 100644
index 0000000..95916f1
Binary files /dev/null and b/images/question-32x32-1bpp.png differ
diff --git a/images/question-32x32-8bpp.png b/images/question-32x32-8bpp.png
new file mode 100644
index 0000000..15dd6f8
Binary files /dev/null and b/images/question-32x32-8bpp.png differ
diff --git a/images/warning-16x16-8bpp.png b/images/warning-16x16-8bpp.png
new file mode 100644
index 0000000..84b8d80
Binary files /dev/null and b/images/warning-16x16-8bpp.png differ
diff --git a/images/warning-32x32-1bpp.png b/images/warning-32x32-1bpp.png
new file mode 100644
index 0000000..463491b
Binary files /dev/null and b/images/warning-32x32-1bpp.png differ
diff --git a/images/warning-32x32-8bpp.png b/images/warning-32x32-8bpp.png
new file mode 100644
index 0000000..74f777f
Binary files /dev/null and b/images/warning-32x32-8bpp.png differ
diff --git a/images/windows-16x16.png b/images/windows-16x16.png
new file mode 100644
index 0000000..cd28533
Binary files /dev/null and b/images/windows-16x16.png differ
diff --git a/images/windows-32x32.png b/images/windows-32x32.png
new file mode 100644
index 0000000..533bbe7
Binary files /dev/null and b/images/windows-32x32.png differ
diff --git a/index.html b/index.html
index 5c7e861..83a1156 100644
--- a/index.html
+++ b/index.html
@@ -396,13 +396,14 @@
 		<script src="lib/imagetracer_v1.2.5.js"></script>
 
 		<script src="src/app-localization.js"></script> <!-- must not be async/deferred, as it uses document.write(); and must come before other app code which uses localization functions -->
+		<script src="src/msgbox.js"></script>
 		<script src="src/functions.js"></script>
 		<script src="src/helpers.js"></script>
 		<script src="src/storage.js"></script>
 		<script src="src/$Component.js"></script>
 		<script src="src/$ToolWindow.js"></script>
 		<script>
-			// after show_error_message, $DialogWindow, and localize are defined,
+			// after show_error_message, showMessageBox, and localize are defined,
 			// set up better global error handling
 			const old_onerror = window.onerror;
 			window.onerror = (message, source, lineno, colno, error)=> {
diff --git a/src/app-localization.js b/src/app-localization.js
index 4d5c86a..4521393 100644
--- a/src/app-localization.js
+++ b/src/app-localization.js
@@ -1088,24 +1088,27 @@ function loaded_localizations(language, mapping) {
 	current_language = language;
 }
 function set_language(language) {
-	const $w = $DialogWindow().title("Reload Required").addClass("dialogue-window");
-	$w.$main.text("The application needs to reload to change the language.");
-	$w.$main.css("max-width", "600px");
-	$w.$Button(localize("OK"), () => {
-		$w.close();
-		are_you_sure(() => {
-			try {
-				localStorage[language_storage_key] = language;
-				location.reload();
-			} catch(error) {
-				show_error_message("Failed to store language preference. Make sure cookies / local storage is enabled in your browser settings.", error);
-			}
-		});
-	}).focus();
-	$w.$Button(localize("Cancel"), () => {
-		$w.close();
+	showMessageBox({
+		title: "Reload Required",
+		message: "The application needs to reload to change the language.",
+		buttons: [
+			{ label: localize("OK"), value: "reload", default: true },
+			{ label: localize("Cancel"), value: "cancel" },
+		],
+		windowOptions: {
+			innerWidth: 450,
+		},
+	}).then((result) => {
+		if (result === "reload") {
+			are_you_sure(() => {
+				try {
+					localStorage[language_storage_key] = language;
+					location.reload();
+				} catch (error) {
+					show_error_message("Failed to store language preference. Make sure cookies / local storage is enabled in your browser settings.", error);
+				}
+			});
+		}
 	});
-	$w.center();
-	// load_language(language);
 }
 load_language(current_language);
\ No newline at end of file
diff --git a/src/app.js b/src/app.js
index 075a122..51339ac 100644
--- a/src/app.js
+++ b/src/app.js
@@ -152,12 +152,12 @@ window.systemHookDefaults = {
 				newFileName = newHandle.name;
 				const newFileExtension = get_file_extension(newFileName);
 				if (!newFileExtension) {
-					show_error_message(`Missing file extension - try adding .${new_format.extensions[0]} to the name.`);
+					show_error_message(`Missing file extension.\n\nTry adding .${new_format.extensions[0]} to the name.`);
 					return;
 				}
 				if (!new_format.extensions.includes(newFileExtension)) {
 					// Closest translation: "Paint cannot save to the same filename with a different file type."
-					show_error_message(`Wrong file extension for selected file type - try adding .${new_format.extensions[0]} to the name.`);
+					show_error_message(`Wrong file extension for selected file type.\n\nTry adding .${new_format.extensions[0]} to the name.`);
 					return;
 				}
 				// const new_format =
diff --git a/src/functions.js b/src/functions.js
index b7317c0..3969223 100644
--- a/src/functions.js
+++ b/src/functions.js
@@ -829,35 +829,32 @@ try {
 	// This will be known as the "Y2T bug"
 	confirmed_overwrite = Date.now() >= 2000000000000;
 }
-function confirm_overwrite() {
-	return new Promise((resolve) => {
-		if (confirmed_overwrite) {
-			resolve();
-			return;
-		}
-		const $w = new $DialogWindow().addClass("dialogue-window");
-		$w.title(localize("Paint"));
-		$w.$main.html(`
+async function confirm_overwrite() {
+	if (confirmed_overwrite) {
+		return;
+	}
+	const { $window, promise } = showMessageBox({
+		messageHTML: `
 			<p>JS Paint can now save over existing files.</p>
 			<p>Do you want to overwrite the file?</p>
 			<p>
 				<label><input type='checkbox'/> Don't ask me again</label>
 			</p>
-		`);
-		$w.$Button(localize("OK"), () => {
-			$w.close();
-			confirmed_overwrite = $w.$main.find("input[type='checkbox']").prop("checked");
-			try {
-				localStorage[confirmed_overwrite_key] = confirmed_overwrite;
-			} catch (error) {
-				// no localStorage
-			}
-		}).focus();
-		$w.$Button(localize("Cancel"), () => {
-			$w.close();
-		});
-		$w.center();
+		`,
+		buttons: [
+			{ label: localize("Yes"), value: "overwrite", default: true },
+			{ label: localize("Cancel"), value: "cancel" },
+		],
 	});
+	const result = await promise;
+	if (result === "overwrite") {
+		confirmed_overwrite = $window.$content.find("input[type='checkbox']").prop("checked");
+		try {
+			localStorage[confirmed_overwrite_key] = confirmed_overwrite;
+		} catch (error) {
+			// no localStorage... @TODO: don't show the checkbox in this case
+		}
+	}
 }
 
 
@@ -908,49 +905,62 @@ function file_save_as(maybe_saved_callback=()=>{}, update_from_saved=true){
 }
 
 
-function are_you_sure(action, canceled){
-	if(saved){
+function are_you_sure(action, canceled) {
+	if (saved) {
 		action();
-	}else{
-		const $w = new $DialogWindow().addClass("dialogue-window");
-		$w.title(localize("Paint"));
-		$w.$main.text(localize("Save changes to %1?", file_name));
-		$w.$Button(localize("Save"), () => {
-			$w.close();
-			file_save(()=> {
+	} else {
+		showMessageBox({
+			message: localize("Save changes to %1?", file_name),
+			buttons: [
+				{
+					// label: localize("Save"),
+					label: localize("Yes"),
+					value: "save",
+					default: true,
+				},
+				{
+					// label: "Discard",
+					label: localize("No"),
+					value: "discard",
+				},
+				{
+					label: localize("Cancel"),
+					value: "cancel",
+				},
+			],
+		}).then((result) => {
+			if (result === "save") {
+				file_save(() => {
+					action();
+				}, false);
+			} else if (result === "discard") {
 				action();
-			}, false);
-		})[0].focus();
-		$w.$Button("Discard", () => {
-			$w.close();
-			action();
+			} else {
+				canceled?.();
+			}
 		});
-		$w.$Button(localize("Cancel"), () => {
-			$w.close();
-			canceled && canceled();
-		});
-		$w.$x.on("click", () => {
-			canceled && canceled();
-		});
-		$w.center();
 	}
 }
 
 function please_enter_a_number() {
-	const $w = new $DialogWindow("Invalid Value").addClass("dialogue-window");
-	$w.$main.text(localize("Please enter a number."));
-	$w.$Button(localize("OK"), () => {
-		$w.close();
-	}).focus();
+	showMessageBox({
+		// title: "Invalid Value",
+		message: localize("Please enter a number."),
+	});
 }
 
-function show_error_message(message, error){
-	const $w = $DialogWindow().title(localize("Paint")).addClass("dialogue-window squish");
-	$w.$main.text(message);
-	$w.$main.css("max-width", "600px");
+function show_error_message(message, error) {
+	const { $message } = showMessageBox({
+		iconID: "error",
+		message,
+		// windowOptions: {
+		// 	innerWidth: 600,
+		// },
+	});
+	// $message.css("max-width", "600px");
 	if(error){
 		const $details = $("<details><summary><span>Details</span></summary></details>")
-		.appendTo($w.$main);
+		.appendTo($message);
 
 		// Chrome includes the error message in the error.stack string, whereas Firefox doesn't.
 		// Also note that there can be Exception objects that don't have a message (empty string) but a name,
@@ -979,25 +989,21 @@ function show_error_message(message, error){
 			overflow: "auto",
 		});
 	}
-	$w.$Button(localize("OK"), () => {
-		$w.close();
-	}).focus();
-	$w.center();
 	if (error) {
-		window.console && console.error(message, error);
+		window.console?.error?.(message, error);
 	} else {
-		window.console && console.error(message);
+		window.console?.error?.(message);
 	}
 }
 
 // @TODO: close are_you_sure windows and these Error windows when switching sessions
 // because it can get pretty confusing
 function show_resource_load_error_message(error){
-	const $w = $DialogWindow().title(localize("Paint")).addClass("dialogue-window");
+	const { $window, $message } = showMessageBox({});
 	const firefox = navigator.userAgent.toLowerCase().indexOf("firefox") > -1;
 	// @TODO: copy & paste vs download & open, more specific guidance
 	if (error.code === "cross-origin-blob-uri") {
-		$w.$main.html(`
+		$message.html(`
 			<p>Can't load image from address starting with "blob:".</p>
 			${
 				firefox ?
@@ -1006,47 +1012,43 @@ function show_resource_load_error_message(error){
 			}
 		`);
 	} else if (error.code === "html-not-image") {
-		$w.$main.html(`
+		$message.html(`
 			<p>Address points to a web page, not an image file.</p>
 			<p>Try copying and pasting an image instead of a URL.</p>
 		`);
 	} else if (error.code === "decoding-failure") {
-		$w.$main.html(`
+		$message.html(`
 			<p>Address doesn't point to an image file of a supported format.</p>
 			<p>Try copying and pasting an image instead of a URL.</p>
 		`);
 	} else if (error.code === "access-failure") {
 		if (navigator.onLine) {
-			$w.$main.html(`
+			$message.html(`
 				<p>Failed to download image.</p>
 				<p>Try copying and pasting an image instead of a URL.</p>
 			`);
 			if (error.fails) {
 				$("<ul>").append(error.fails.map(({status, statusText, url})=>
 					$("<li>").text(url).prepend($("<b>").text(`${status || ""} ${statusText || "Failed"} `))
-				)).appendTo($w.$main);
+				)).appendTo($message);
 			}
 		} else {
-			$w.$main.html(`
+			$message.html(`
 				<p>Failed to download image.</p>
 				<p>You're offline. Connect to the internet and try again.</p>
 				<p>Or copy and paste an image instead of a URL, if possible.</p>
 			`);
 		}
 	} else {
-		$w.$main.html(`
+		$message.html(`
 			<p>Failed to load image from URL.</p>
 			<p>Check your browser's devtools for details.</p>
 		`);
 	}
-	$w.$main.css({maxWidth: "500px"});
-	$w.$Button(localize("OK"), () => {
-		$w.close();
-	}).focus();
-	$w.center();
+	$message.css({ maxWidth: "500px" });
+	$window.center(); // after adding content
 }
 function show_file_format_errors({ as_image_error, as_palette_error }) {
-	const $w = $DialogWindow().title(localize("Paint")).addClass("dialogue-window");
 	let html = `
 		<p>${localize("Paint cannot open this file.")}</p>
 	`;
@@ -1096,10 +1098,9 @@ function show_file_format_errors({ as_image_error, as_palette_error }) {
 			</details>
 		`;
 	}
-	$w.$main.html(html);
-	$w.$Button(localize("OK"), () => {
-		$w.close();
-	}).focus();
+	showMessageBox({
+		messageHTML: html,
+	});
 }
 function show_read_image_file_error(error) {
 	// @TODO: similar friendly messages to show_resource_load_error_message,
@@ -1300,34 +1301,50 @@ async function choose_file_to_paste() {
 function paste(img_or_canvas){
 
 	if(img_or_canvas.width > main_canvas.width || img_or_canvas.height > main_canvas.height){
-		const $w = new $DialogWindow().addClass("dialogue-window");
-		$w.title(localize("Paint"));
-		$w.$main.html(`
-			${localize("The image in the clipboard is larger than the bitmap.")}<br>
-			${localize("Would you like the bitmap enlarged?")}<br>
-		`);
-		$w.$Button("Enlarge", () => {
-			$w.close();
-			// The resize gets its own undoable, as in mspaint
-			resize_canvas_and_save_dimensions(
-				Math.max(main_canvas.width, img_or_canvas.width),
-				Math.max(main_canvas.height, img_or_canvas.height),
+		showMessageBox({
+			message: localize("The image in the clipboard is larger than the bitmap.") + "\n" +
+				localize("Would you like the bitmap enlarged?"),
+			iconID: "question",
+			windowOptions: {
+				icons: {
+					16: "images/windows-16x16.png",
+					32: "images/windows-32x32.png",
+				},
+			},
+			buttons: [
 				{
-					name: "Enlarge Canvas For Paste",
-					icon: get_help_folder_icon("p_stretch_both.png"),
-				}
-			);
-			do_the_paste();
-			$canvas_area.trigger("resize");
-		})[0].focus();
-		$w.$Button("Crop", () => {
-			$w.close();
-			do_the_paste();
+					// label: "Enlarge",
+					label: localize("Yes"),
+					value: "enlarge",
+					default: true,
+				},
+				{
+					// label: "Crop",
+					label: localize("No"),
+					value: "crop",
+				},
+				{
+					label: localize("Cancel"),
+					value: "cancel",
+				},
+			],
+		}).then((result) => {
+			if (result === "enlarge") {
+				// The resize gets its own undoable, as in mspaint
+				resize_canvas_and_save_dimensions(
+					Math.max(main_canvas.width, img_or_canvas.width),
+					Math.max(main_canvas.height, img_or_canvas.height),
+					{
+						name: "Enlarge Canvas For Paste",
+						icon: get_help_folder_icon("p_stretch_both.png"),
+					}
+				);
+				do_the_paste();
+				$canvas_area.trigger("resize");
+			} else if (result === "crop") {
+				do_the_paste();
+			}
 		});
-		$w.$Button(localize("Cancel"), () => {
-			$w.close();
-		});
-		$w.center();
 	}else{
 		do_the_paste();
 	}
@@ -1647,6 +1664,7 @@ function undo(){
 	return true;
 }
 
+// @TODO: use Clippy.js instead for potentially annoying tips
 let $document_history_prompt_window;
 function redo(){
 	if(redos.length<1){
@@ -1654,13 +1672,11 @@ function redo(){
 			$document_history_prompt_window.close();
 		}
 		if (!$document_history_window || $document_history_window.closed) {
-			const $w = $document_history_prompt_window = new $DialogWindow();
-			$w.title("Redo");
-			$w.$main.html("To view all branches of the history tree, click <b>Edit > History</b>.").css({padding: 10});
-			// $w.$Button("Show History", show_document_history).css({margin: 10}).focus();
-			// $w.$Button(localize("Cancel"), ()=> { $w.close(); }).css({margin: 10});
-			$w.$Button(localize("OK"), ()=> { $w.close(); }).css({margin: 10}).focus();
-			$w.center();
+			$document_history_prompt_window = showMessageBox({
+				title: "Redo",
+				messageHTML: `To view all branches of the history tree, click <b>Edit > History</b>.`,
+				iconID: "info",
+			}).$window;
 		}
 		return false;
 	}
@@ -3196,18 +3212,16 @@ function sanity_check_blob(blob, okay_callback, magic_number_bytes, magic_wanted
 				if (magic_found === magic_wanted) {
 					okay_callback();
 				} else {
-					const $w = $DialogWindow().title(localize("Paint")).addClass("dialogue-window");
-					// hackily combining messages that are already localized
-					// you have to do some deduction to understand this message
-					$w.$main.html(`
-						<p>${localize("Unexpected file format.")}</p>
-						<p>${localize("An unsupported operation was attempted.")}</p>
-					`);
-					$w.$main.css({maxWidth: "500px"});
-					$w.$Button(localize("OK"), () => {
-						$w.close();
-					}).focus();
-					$w.center();
+					showMessageBox({
+						// hackily combining messages that are already localized, in ways they were not meant to be used.
+						// you may have to do some deduction to understand this message.
+						// messageHTML: `
+						// 	<p>${localize("Unexpected file format.")}</p>
+						// 	<p>${localize("An unsupported operation was attempted.")}</p>
+						// `,
+						message: "Your browser does not support writing images in this file format.",
+						iconID: "error",
+					});
 				}
 			}, (error)=> {
 				show_error_message(localize("An unknown error has occurred."), error);
diff --git a/src/help.js b/src/help.js
index fdc4e3e..39e2bf8 100644
--- a/src/help.js
+++ b/src/help.js
@@ -255,17 +255,19 @@ function open_help_viewer(options){
 	}, (/* error */)=> {
 		// access to error message is not allowed either, basically
 		if (location.protocol === "file:") {
-			const $w = $DialogWindow().title(localize("Paint")).addClass("dialogue-window");
-			$w.$main.html(`
-				<p>${localize("Failed to launch help.")}</p>
-				<p>This feature is not available when running from the <code>file:</code> protocol.</p>
-				<p>To use this feature, start a web server. If you have Python, you can use <code>python -m SimpleHTTPServer</code></p>
-			`);
-			$w.$main.css({maxWidth: "500px"});
-			$w.$Button(localize("OK"), () => {
-				$w.close();
-			}).focus();
-			$w.center();
+			showMessageBox({
+				// <p>${localize("Failed to launch help.")}</p>
+				// but it's already launched at this point
+
+				// what's a good tutorial for starting a web server?
+				// https://gist.github.com/willurd/5720255 - impressive list, but not a tutorial
+				// https://attacomsian.com/blog/local-web-server - OK, good enough
+				messageHTML: `
+					<p>Help is not available when running from the <code>file:</code> protocol.</p>
+					<p>To use this feature, <a href="https://attacomsian.com/blog/local-web-server">start a web server</a>.</p>
+				`,
+				iconID: "error",
+			});
 		} else {
 			show_error_message(`${localize("Failed to launch help.")} ${localize("Access to %1 was denied.", options.contentsFile)}`);
 		}
diff --git a/src/manage-storage.js b/src/manage-storage.js
index cf711be..b781145 100644
--- a/src/manage-storage.js
+++ b/src/manage-storage.js
@@ -3,7 +3,7 @@ let $storage_manager;
 let $quota_exceeded_window;
 let ignoring_quota_exceeded = false;
 
-function storage_quota_exceeded(){
+async function storage_quota_exceeded(){
 	if($quota_exceeded_window){
 		$quota_exceeded_window.close();
 		$quota_exceeded_window = null;
@@ -11,27 +11,27 @@ function storage_quota_exceeded(){
 	if(ignoring_quota_exceeded){
 		return;
 	}
-	const $w = $DialogWindow().title("Storage Error").addClass("dialogue-window squish");
-	$w.$main.html(
-		"<p>JS Paint stores images as you work on them so that if you " +
-		"close your browser or tab or reload the page " +
-		"your images are usually safe.</p>" +
-		"<p>However, it has run out of space to do so.</p>" +
-		"<p>You can still save the current image with <b>File > Save</b>. " +
-		"You should save frequently, or free up enough space to keep the image safe.</p>"
-	);
-	$w.$Button("Manage Storage", () => {
-		$w.close();
+	const { promise, $window } = showMessageBox({
+		title: "Storage Error",
+		messageHTML: `
+			<p>JS Paint stores images as you work on them so that if you close your browser or tab or reload the page your images are usually safe.</p>
+			<p>However, it has run out of space to do so.</p>
+			<p>You can still save the current image with <b>File > Save</b>. You should save frequently, or free up enough space to keep the image safe.</p>
+		`,
+		buttons: [
+			{ label: "Manage Storage", value: "manage", default: true },
+			{ label: "Ignore", value: "ignore" },
+		],
+		iconID: "warning",
+	});
+	$quota_exceeded_window = $window;
+	const result = await promise;
+	if (result === "ignore") {
+		ignoring_quota_exceeded = true;
+	} else if (result === "manage") {
 		ignoring_quota_exceeded = false;
 		manage_storage();
-	}).focus();
-	$w.$Button("Ignore", () => {
-		$w.close();
-		ignoring_quota_exceeded = true;
-	});
-	$w.$content.width(500);
-	$w.center();
-	$quota_exceeded_window = $w;
+	}
 }
 
 function manage_storage(){
diff --git a/src/msgbox.js b/src/msgbox.js
new file mode 100644
index 0000000..e02ef1c
--- /dev/null
+++ b/src/msgbox.js
@@ -0,0 +1,105 @@
+
+// Prefer a function injected from outside an iframe,
+// which will make dialogs that can go outside the iframe,
+// for 98.js.org integration.
+// Note that this API must be kept in sync with the version in 98.js.org.
+
+// Note `defaultMessageBoxTitle` handling in make_iframe_window
+// Any other default parameters need to be handled there (as it works now)
+
+window.defaultMessageBoxTitle = localize("Paint");
+
+var chord_audio = new Audio("audio/chord.wav");
+
+window.showMessageBox = window.showMessageBox || (({
+	title = window.defaultMessageBoxTitle ?? "Alert",
+	message,
+	messageHTML,
+	buttons = [{ label: "OK", value: "ok", default: true }],
+	iconID = "warning", // "error", "warning", "info", or "nuke" for deleting files/folders
+	windowOptions = {}, // for controlling width, etc.
+}) => {
+	let $window, $message;
+	const promise = new Promise((resolve, reject) => {
+		$window = make_window_supporting_scale(Object.assign({
+			title,
+			resizable: false,
+			innerWidth: 400,
+			maximizeButton: false,
+			minimizeButton: false,
+		}, windowOptions));
+		// $window.addClass("dialogue-window");
+		$message =
+			$("<div>").css({
+				textAlign: "left",
+				fontFamily: "MS Sans Serif, Arial, sans-serif",
+				fontSize: "14px",
+				marginTop: "22px",
+				flex: 1,
+				minWidth: 0, // Fixes hidden overflow, see https://css-tricks.com/flexbox-truncated-text/
+				whiteSpace: "normal", // overriding .window:not(.squish)
+			});
+		if (messageHTML) {
+			$message.html(messageHTML);
+		} else if (message) { // both are optional because you may populate later with dynamic content
+			$message.text(message).css({
+				whiteSpace: "pre-wrap",
+				wordWrap: "break-word",
+			});
+		}
+		$("<div>").append(
+			$("<img width='32' height='32'>").attr("src", `images/${iconID}-32x32-8bpp.png`).css({
+				margin: "16px",
+				display: "block",
+			}),
+			$message
+		).css({
+			display: "flex",
+			flexDirection: "row",
+		}).appendTo($window.$content);
+
+		$window.$content.css({
+			textAlign: "center",
+		});
+		for (const button of buttons) {
+			const $button = $window.$Button(button.label, () => {
+				button.action?.(); // API may be required for using user gesture requiring APIs
+				resolve(button.value);
+				$window.close(); // actually happens automatically
+			});
+			if (button.default) {
+				$button.addClass("default");
+				$button.focus();
+				setTimeout(() => $button.focus(), 0); // @TODO: why is this needed? does it have to do with the iframe window handling?
+			}
+			$button.css({
+				minWidth: 75,
+				height: 23,
+				margin: "16px 2px",
+			});
+		}
+		$window.on("focusin", "button", (event) => {
+			$(event.currentTarget).addClass("default");
+		});
+		$window.on("focusout", "button", (event) => {
+			$(event.currentTarget).removeClass("default");
+		});
+		$window.on("closed", () => {
+			resolve("closed"); // or "cancel"? do you need to distinguish?
+		});
+		$window.center();
+	});
+	promise.$window = $window;
+	promise.$message = $message;
+	promise.promise = promise; // for easy destructuring
+	try {
+		chord_audio.play();
+	} catch (error) {
+		console.log(`Failed to play ${chord_audio.src}: `, error);
+	}
+	return promise;
+});
+
+window.alert = (message) => {
+	showMessageBox({ message });
+};
diff --git a/src/sessions.js b/src/sessions.js
index 969da9f..7eb360d 100644
--- a/src/sessions.js
+++ b/src/sessions.js
@@ -233,20 +233,17 @@
 		}
 		start() {
 			// @TODO: how do you actually detect if it's failing???
-			const $w = $DialogWindow().title(localize("Paint")).addClass("dialogue-window");
-			$w.$main.html("<p>The document may not load. Changes may not save.</p>" +
-				"<p>Multiuser sessions are public. There is no security.</p>"
-				// "<p>The document may not load. Changes may not save. If it does save, it's public. There is no security.</p>"// +
-				// "<p>I haven't found a way to detect Firebase quota limits being exceeded, " +
-				// "so for now I'm showing this message regardless of whether it's working.</p>" +
-				// "<p>If you're interested in using multiuser mode, please thumbs-up " +
-				// "<a href='https://github.com/1j01/jspaint/issues/68'>this issue</a> to show interest, and/or subscribe for updates.</p>"
-			);
-			$w.$main.css({ maxWidth: "500px" });
-			$w.$Button(localize("OK"), () => {
-				$w.close();
-			}).focus();
-			$w.center();
+			showMessageBox({
+				messageHTML: `
+					<p>The document may not load. Changes may not save.</p>
+					<p>Multiuser sessions are public. There is no security.</p>
+				`
+			});
+			// "<p>The document may not load. Changes may not save. If it does save, it's public. There is no security.</p>"// +
+			// "<p>I haven't found a way to detect Firebase quota limits being exceeded, " +
+			// "so for now I'm showing this message regardless of whether it's working.</p>" +
+			// "<p>If you're interested in using multiuser mode, please thumbs-up " +
+			// "<a href='https://github.com/1j01/jspaint/issues/68'>this issue</a> to show interest, and/or subscribe for updates.</p>"
 			
 			// Wrap the Firebase API because they don't
 			// provide a great way to clean up event listeners