diff --git a/src/components/App/index.tsx b/src/components/App/index.tsx
index fd5006f7..3aa34cb0 100644
--- a/src/components/App/index.tsx
+++ b/src/components/App/index.tsx
@@ -4,7 +4,7 @@ import { bind, linkRef, Fileish } from '../../lib/initial-util';
 import * as style from './style.scss';
 import { FileDropEvent } from './custom-els/FileDrop';
 import './custom-els/FileDrop';
-import SnackBarElement from '../../lib/SnackBar';
+import SnackBarElement, { SnackOptions } from '../../lib/SnackBar';
 import '../../lib/SnackBar';
 import Intro from '../intro';
 import '../custom-els/LoadingSpinner';
@@ -39,7 +39,7 @@ export default class App extends Component<Props, State> {
     import('../compress').then((module) => {
       this.setState({ Compress: module.default });
     }).catch(() => {
-      this.showError('Failed to load app');
+      this.showSnack('Failed to load app');
     });
 
     // In development, persist application state across hot reloads:
@@ -66,9 +66,9 @@ export default class App extends Component<Props, State> {
   }
 
   @bind
-  private showError(error: string) {
+  private showSnack(message: string, options: SnackOptions = {}): Promise<string> {
     if (!this.snackbar) throw Error('Snackbar missing');
-    this.snackbar.showSnackbar({ message: error });
+    return this.snackbar.showSnackbar(message, options);
   }
 
   render({}: Props, { file, Compress }: State) {
@@ -76,9 +76,9 @@ export default class App extends Component<Props, State> {
       <div id="app" class={style.app}>
         <file-drop accept="image/*" onfiledrop={this.onFileDrop} class={style.drop}>
           {(!file)
-            ? <Intro onFile={this.onIntroPickFile} onError={this.showError} />
+            ? <Intro onFile={this.onIntroPickFile} showSnack={this.showSnack} />
             : (Compress)
-              ? <Compress file={file} onError={this.showError} />
+              ? <Compress file={file} showSnack={this.showSnack} />
               : <loading-spinner class={style.appLoader}/>
           }
           <snack-bar ref={linkRef(this, 'snackbar')} />
diff --git a/src/components/compress/index.tsx b/src/components/compress/index.tsx
index 0e54ad09..ef5f19aa 100644
--- a/src/components/compress/index.tsx
+++ b/src/components/compress/index.tsx
@@ -35,6 +35,7 @@ import { VectorResizeOptions, BitmapResizeOptions } from '../../codecs/resize/pr
 import './custom-els/MultiPanel';
 import Results from '../results';
 import { ExpandIcon, CopyAcrossIconProps } from '../../lib/icons';
+import SnackBarElement from 'src/lib/SnackBar';
 
 export interface SourceImage {
   file: File | Fileish;
@@ -58,7 +59,7 @@ interface EncodedImage {
 
 interface Props {
   file: File | Fileish;
-  onError: (msg: string) => void;
+  showSnack: SnackBarElement['showSnackbar'];
 }
 
 interface State {
@@ -250,12 +251,24 @@ export default class Compress extends Component<Props, State> {
     }
   }
 
-  private onCopyToOtherClick(index: 0 | 1) {
+  private async onCopyToOtherClick(index: 0 | 1) {
     const otherIndex = (index + 1) % 2;
+    const oldSettings = this.state.images[otherIndex];
 
     this.setState({
       images: cleanSet(this.state.images, otherIndex, this.state.images[index]),
     });
+
+    const result = await this.props.showSnack('Settings copied across', {
+      timeout: 5000,
+      actions: ['undo', 'dismiss'],
+    });
+
+    if (result !== 'undo') return;
+
+    this.setState({
+      images: cleanSet(this.state.images, otherIndex, oldSettings),
+    });
   }
 
   @bind
@@ -318,7 +331,7 @@ export default class Compress extends Component<Props, State> {
       console.error(err);
       // Another file has been opened before this one processed.
       if (this.state.loadingCounter !== loadingCounter) return;
-      this.props.onError('Invalid image');
+      this.props.showSnack('Invalid image');
       this.setState({ loading: false });
     }
   }
@@ -377,7 +390,7 @@ export default class Compress extends Component<Props, State> {
         }
       } catch (err) {
         if (err.name === 'AbortError') return;
-        this.props.onError(`Processing error (type=${image.encoderState.type}): ${err}`);
+        this.props.showSnack(`Processing error (type=${image.encoderState.type}): ${err}`);
         throw err;
       }
     }
diff --git a/src/components/intro/index.tsx b/src/components/intro/index.tsx
index f99d8b23..89dbb03a 100644
--- a/src/components/intro/index.tsx
+++ b/src/components/intro/index.tsx
@@ -12,6 +12,7 @@ import artworkIcon from './imgs/demos/artwork-icon.jpg';
 import deviceScreenIcon from './imgs/demos/device-screen-icon.jpg';
 import logoIcon from './imgs/demos/logo-icon.png';
 import * as style from './style.scss';
+import SnackBarElement from '../../lib/SnackBar';
 
 const demos = [
   {
@@ -42,7 +43,7 @@ const demos = [
 
 interface Props {
   onFile: (file: File | Fileish) => void;
-  onError: (error: string) => void;
+  showSnack: SnackBarElement['showSnackbar'];
 }
 interface State {
   fetchingDemoIndex?: number;
@@ -79,7 +80,7 @@ export default class Intro extends Component<Props, State> {
       this.props.onFile(file);
     } catch (err) {
       this.setState({ fetchingDemoIndex: undefined });
-      this.props.onError("Couldn't fetch demo image");
+      this.props.showSnack("Couldn't fetch demo image");
     }
   }
 
diff --git a/src/lib/SnackBar/index.ts b/src/lib/SnackBar/index.ts
index 759306bc..8e55eabc 100644
--- a/src/lib/SnackBar/index.ts
+++ b/src/lib/SnackBar/index.ts
@@ -1,114 +1,96 @@
-import './styles.css';
-
-const DEFAULT_TIMEOUT = 2750;
+import * as style from './styles.css';
 
 export interface SnackOptions {
-  message: string;
   timeout?: number;
-  actionText?: string;
-  actionHandler?: () => boolean | null;
+  actions?: string[];
 }
 
-export interface SnackShowResult {
-  action: boolean;
-}
+function createSnack(message: string, options: SnackOptions): [Element, Promise<string>] {
+  const {
+    timeout = 0,
+    actions = [],
+  } = options;
 
-class Snack {
-  private _onremove: ((result: SnackShowResult) => void)[] = [];
-  private _options: SnackOptions;
-  private _element: Element = document.createElement('div');
-  private _text: Element = document.createElement('div');
-  private _button: Element = document.createElement('button');
-  private _showing = false;
-  private _closeTimer?: number;
-  private _result: SnackShowResult = {
-    action: false,
-  };
+  // Provide a default 'dismiss' action
+  if (!timeout && actions.length === 0) actions.push('dismiss');
 
-  constructor (options: SnackOptions, callback?: (result: SnackShowResult) => void) {
-    this._options = options;
+  const el = document.createElement('div');
+  el.className = style.snackbar;
+  el.setAttribute('aria-live', 'assertive');
+  el.setAttribute('aria-atomic', 'true');
+  el.setAttribute('aria-hidden', 'false');
 
-    this._element.className = 'snackbar';
-    this._element.setAttribute('aria-live', 'assertive');
-    this._element.setAttribute('aria-atomic', 'true');
-    this._element.setAttribute('aria-hidden', 'true');
+  const text = document.createElement('div');
+  text.className = style.text;
+  text.textContent = message;
+  el.appendChild(text);
 
-    this._text.className = 'snackbar--text';
-    this._text.textContent = options.message;
-    this._element.appendChild(this._text);
+  const result = new Promise<string>((resolve) => {
+    let timeoutId: number;
 
-    if (options.actionText) {
-      this._button.className = 'snackbar--button';
-      this._button.textContent = options.actionText;
-      this._button.addEventListener('click', () => {
-        if (this._showing) {
-          if (options.actionHandler && options.actionHandler() === false) return;
-          this._result.action = true;
-        }
-        this.hide();
+    // Add action buttons
+    for (const action of actions) {
+      const button = document.createElement('button');
+      button.className = style.button;
+      button.textContent = action;
+      button.addEventListener('click', () => {
+        clearTimeout(timeoutId);
+        resolve(action);
       });
-      this._element.appendChild(this._button);
+      el.appendChild(button);
     }
 
-    if (callback) {
-      this._onremove.push(callback);
+    // Add timeout
+    if (timeout) {
+      timeoutId = self.setTimeout(
+        () => resolve(''),
+        timeout,
+      );
     }
-  }
+  });
 
-  cancelTimer () {
-    if (this._closeTimer != null) clearTimeout(this._closeTimer);
-  }
-
-  show (parent: Element): Promise<SnackShowResult> {
-    if (this._showing) return Promise.resolve(this._result);
-    this._showing = true;
-    this.cancelTimer();
-    if (parent !== this._element.parentNode) {
-      parent.appendChild(this._element);
-    }
-    this._element.removeAttribute('aria-hidden');
-    this._closeTimer = setTimeout(this.hide.bind(this), this._options.timeout || DEFAULT_TIMEOUT);
-    return new Promise((resolve) => {
-      this._onremove.push(resolve);
-    });
-  }
-
-  hide () {
-    if (!this._showing) return;
-    this._showing = false;
-    this.cancelTimer();
-    this._element.addEventListener('animationend', this.remove.bind(this));
-    this._element.setAttribute('aria-hidden', 'true');
-  }
-
-  remove () {
-    this.cancelTimer();
-    const parent = this._element.parentNode;
-    if (parent) parent.removeChild(this._element);
-    this._onremove.forEach(f => f(this._result));
-    this._onremove = [];
-  }
+  return [el, result];
 }
 
 export default class SnackBarElement extends HTMLElement {
-  private _snackbars: Snack[] = [];
-  private _processingStack = false;
+  private _snackbars: [string, SnackOptions, (action: Promise<string>) => void][] = [];
+  private _processingQueue = false;
 
-  showSnackbar (options: SnackOptions): Promise<SnackShowResult> {
-    return new Promise((resolve) => {
-      const snack = new Snack(options, resolve);
-      this._snackbars.push(snack);
-      this._processStack();
+  /**
+   * Show a snackbar. Returns a promise for the name of the action clicked, or an empty string if no
+   * action is clicked.
+   */
+  showSnackbar(message: string, options: SnackOptions = {}): Promise<string> {
+    return new Promise<string>((resolve) => {
+      this._snackbars.push([message, options, resolve]);
+      if (!this._processingQueue) this._processQueue();
     });
   }
 
-  private async _processStack () {
-    if (this._processingStack === true || this._snackbars.length === 0) return;
-    this._processingStack = true;
-    await this._snackbars[0].show(this);
-    this._snackbars.shift();
-    this._processingStack = false;
-    this._processStack();
+  private async _processQueue() {
+    this._processingQueue = true;
+
+    while (this._snackbars[0]) {
+      const [message, options, resolver] = this._snackbars[0];
+      const [el, result] = createSnack(message, options);
+      // Pass the result back to the original showSnackbar call.
+      resolver(result);
+      this.appendChild(el);
+
+      // Wait for the user to click an action, or for the snack to timeout.
+      await result;
+
+      // Transition the snack away.
+      el.setAttribute('aria-hidden', 'true');
+      await new Promise((resolve) => {
+        el.addEventListener('animationend', () => resolve());
+      });
+      el.remove();
+
+      this._snackbars.shift();
+    }
+
+    this._processingQueue = false;
   }
 }
 
diff --git a/src/lib/SnackBar/styles.css b/src/lib/SnackBar/styles.css
index be02ecd4..c1ece455 100644
--- a/src/lib/SnackBar/styles.css
+++ b/src/lib/SnackBar/styles.css
@@ -22,7 +22,6 @@ snack-bar {
   transform-origin: center;
   color: #eee;
   z-index: 100;
-  pointer-events: none;
   cursor: default;
   will-change: transform;
   animation: snackbar-show 300ms ease forwards 1;
@@ -53,13 +52,13 @@ snack-bar {
   }
 }
 
-.snackbar--text {
+.text {
   flex: 1 1 auto;
   padding: 16px;
   font-size: 100%;
 }
 
-.snackbar--button {
+.button {
   position: relative;
   flex: 0 1 auto;
   padding: 8px;
@@ -75,16 +74,15 @@ snack-bar {
   font-size: 100%;
   text-transform: uppercase;
   text-align: center;
-  pointer-events: all;
   cursor: pointer;
   overflow: hidden;
   transition: background-color 200ms ease;
   outline: none;
 }
-.snackbar--button:hover {
+.button:hover {
   background-color: rgba(0,0,0,0.15);
 }
-.snackbar--button:focus:before {
+.button:focus:before {
   content: '';
   position: absolute;
   left: 50%;
diff --git a/webpack.config.js b/webpack.config.js
index ff942630..6b753b9f 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -25,6 +25,7 @@ module.exports = function (_, env) {
     path.join(__dirname, 'src/components'),
     path.join(__dirname, 'src/codecs'),
     path.join(__dirname, 'src/custom-els'),
+    path.join(__dirname, 'src/lib'),
   ];
 
   return {
@@ -107,7 +108,7 @@ module.exports = function (_, env) {
               loader: 'typings-for-css-modules-loader',
               options: {
                 modules: true,
-                localIdentName: '[local]__[hash:base64:5]',
+                localIdentName: isProd ? '[hash:base64:5]' : '[local]__[hash:base64:5]',
                 namedExport: true,
                 camelCase: true,
                 importLoaders: 1,
@@ -199,8 +200,11 @@ module.exports = function (_, env) {
 
       new OptimizeCssAssetsPlugin({
         cssProcessorOptions: {
-          zindex: false,
-          discardComments: { removeAll: true }
+          postcssReduceIdents: {
+            counterStyle: false,
+            gridTemplate: false,
+            keyframes: false
+          }
         }
       }),