diff --git a/css/ui.css b/css/ui.css
index ce0ba4bd..0e7b5fa6 100644
--- a/css/ui.css
+++ b/css/ui.css
@@ -802,9 +802,8 @@ div.scripting-editor {
   max-height: 50vw;
 }
 div.scripting-color {
-  padding: 0.5em;
-  min-width: 3em;
-  min-height: 3em;
+  min-width: 2em;
+  min-height: 2em;
   border: 3px solid black;
 }
 div.scripting-color span {
@@ -836,3 +835,14 @@ div.scripting-select > .scripting-selected {
   border-style: solid;
   border-color: #eee;
 }
+div.scripting-cell button {
+  background-color: #333;
+  color: #fff;
+  padding: 0.5em;
+}
+div.scripting-cell button:hover {
+  border-color: #fff;
+}
+div.scripting-cell button.scripting-enabled {
+  background-color: #339999;
+}
\ No newline at end of file
diff --git a/src/common/script/env.ts b/src/common/script/env.ts
index 8d3051a5..13950138 100644
--- a/src/common/script/env.ts
+++ b/src/common/script/env.ts
@@ -192,7 +192,7 @@ export class Environment {
             function prkey() { return fullkey.join('.') }
             // go through all object properties recursively
             for (var [key, value] of Object.entries(o)) {
-                if (value == null && fullkey.length == 0 && !key.startsWith("$$")) {
+                if (value == null && fullkey.length == 0 && !key.startsWith("$")) {
                     this.error(key, `"${key}" has no value.`)
                 }
                 fullkey.push(key);
@@ -244,10 +244,22 @@ export class Environment {
                 start: loc.column,
             }]
         }
-        // TODO: Cannot parse given Error object
+        // TODO: Cannot parse given Error object?
         let frames = ErrorStackParser.parse(e);
         let frame = frames.findIndex(f => f.functionName === 'anonymous');
         let errors = [];
+        // if ErrorStackParser fails, resort to regex
+        if (frame < 0 && e.stack != null) {
+            let m = /.anonymous.:(\d+):(\d+)/g.exec(e.stack);
+            if (m != null) {
+                errors.push( {
+                    path: this.path,
+                    msg: e.message,
+                    line: parseInt(m[1]) - LINE_NUMBER_OFFSET,
+                });
+            }
+        }
+        // otherwise iterate thru all the frames
         while (frame >= 0) {
             console.log(frames[frame]);
             if (frames[frame].fileName.endsWith('Function')) {
@@ -261,6 +273,7 @@ export class Environment {
             }
             --frame;
         }
+        // if no stack frames parsed, last resort error msg
         if (errors.length == 0) {
             errors.push( {
                 path: this.path,
diff --git a/src/common/script/lib/bitmap.ts b/src/common/script/lib/bitmap.ts
index 15f1c2b7..187e00e1 100644
--- a/src/common/script/lib/bitmap.ts
+++ b/src/common/script/lib/bitmap.ts
@@ -4,7 +4,7 @@ import * as fastpng from 'fast-png';
 import { Palette } from './color';
 import * as io from './io'
 import * as color from './color'
-import { findIntegerFactors, RGBA } from '../../util';
+import { coerceToArray, findIntegerFactors, RGBA } from '../../util';
 
 export type PixelMapFunction = (x: number, y: number) => number;
 
@@ -17,17 +17,16 @@ export abstract class AbstractBitmap<T> {
         public readonly height: number,
     ) {
     }
-
     abstract blank(width: number, height: number) : AbstractBitmap<T>;
-    abstract setarray(arr: ArrayLike<number>) : AbstractBitmap<T>;
-    abstract set(x: number, y: number, val: number) : AbstractBitmap<T>;
+    abstract setarray(arr: ArrayLike<number>) : void;
+    abstract set(x: number, y: number, val: number) : void;
     abstract get(x: number, y: number): number;
     abstract getrgba(x: number, y: number): number;
 
     inbounds(x: number, y: number): boolean {
         return (x >= 0 && x < this.width && y >= 0 && y < this.height);
     }
-    assign(fn: ArrayLike<number> | PixelMapFunction) {
+    assign(fn: ArrayLike<number> | PixelMapFunction) : void {
         if (typeof fn === 'function') {
             for (let y=0; y<this.height; y++) {
                 for (let x=0; x<this.width; x++) {
@@ -39,10 +38,11 @@ export abstract class AbstractBitmap<T> {
         } else {
             throw new Error(`Illegal argument to assign(): ${fn}`)
         }
-        return this;
     }
     clone() : AbstractBitmap<T> {
-        return this.blank(this.width, this.height).assign((x,y) => this.get(x,y));
+        let bmp = this.blank(this.width, this.height);
+        bmp.assign((x,y) => this.get(x,y));
+        return bmp;
     }
     crop(srcx: number, srcy: number, width: number, height: number) {
         let dest = this.blank(width, height);
@@ -64,6 +64,13 @@ export abstract class AbstractBitmap<T> {
             }
         }
     }
+    fill(destx: number, desty: number, width:number, height:number, value:number) {
+        for (var y=0; y<height; y++) {
+            for (var x=0; x<width; x++) {
+                this.set(x+destx, y+desty, value);
+            }
+        }
+    }
 }
 
 export class RGBABitmap extends AbstractBitmap<RGBABitmap> {
@@ -80,11 +87,9 @@ export class RGBABitmap extends AbstractBitmap<RGBABitmap> {
     }
     setarray(arr: ArrayLike<number>) {
         this.rgba.set(arr);
-        return this;
     }
     set(x: number, y: number, rgba: number) {
         if (this.inbounds(x,y)) this.rgba[y * this.width + x] = rgba;
-        return this;
     }
     get(x: number, y: number): number {
         return this.inbounds(x,y) ? this.rgba[y * this.width + x] : 0;
@@ -92,8 +97,8 @@ export class RGBABitmap extends AbstractBitmap<RGBABitmap> {
     getrgba(x: number, y: number): number {
         return this.get(x, y);
     }
-    blank(width: number, height: number) : RGBABitmap {
-        return new RGBABitmap(width, height);
+    blank(width?: number, height?: number) : RGBABitmap {
+        return new RGBABitmap(width || this.width, height || this.height);
     }
     clone() : RGBABitmap {
         let bitmap = this.blank(this.width, this.height);
@@ -108,47 +113,55 @@ export abstract class MappedBitmap extends AbstractBitmap<MappedBitmap> {
     constructor(
         width: number,
         height: number,
-        public readonly bitsPerPixel: number,
+        public readonly bpp: number,
         initial?: Uint8Array | PixelMapFunction
     ) {
         super(width, height);
-        if (bitsPerPixel != 1 && bitsPerPixel != 2 && bitsPerPixel != 4 && bitsPerPixel != 8)
-            throw new Error(`Invalid bits per pixel: ${bitsPerPixel}`);
+        if (bpp != 1 && bpp != 2 && bpp != 4 && bpp != 8)
+            throw new Error(`Invalid bits per pixel: ${bpp}`);
         this.pixels = new Uint8Array(this.width * this.height);
         if (initial) this.assign(initial);
     }
     setarray(arr: ArrayLike<number>) {
         this.pixels.set(arr);
-        return this;
     }
     set(x: number, y: number, index: number) {
         if (this.inbounds(x,y)) this.pixels[y * this.width + x] = index;
-        return this;
     }
     get(x: number, y: number): number {
         return this.inbounds(x,y) ? this.pixels[y * this.width + x] : 0;
     }
 }
 
+function getbpp(x : number | Palette) : number {
+    if (typeof x === 'number') return x;
+    if (x instanceof Palette) {
+        if (x.colors.length <= 2) return 1;
+        else if (x.colors.length <= 4) return 2;
+        else if (x.colors.length <= 16) return 4;
+    }
+    return 8;
+}
+
 export class IndexedBitmap extends MappedBitmap {
     public palette: Palette;
 
     constructor(
         width: number,
         height: number,
-        bitsPerPixel: number,
+        bppOrPalette: number | Palette,
         initial?: Uint8Array | PixelMapFunction
     ) {
-        super(width, height, bitsPerPixel || 8, initial);
-        this.palette = color.palette.colors(1 << this.bitsPerPixel);
+        super(width, height, getbpp(bppOrPalette), initial);
+        this.palette = bppOrPalette instanceof Palette
+            ? bppOrPalette 
+            : color.palette.colors(1 << this.bpp);
     }
-
     getrgba(x: number, y: number): number {
         return this.palette && this.palette.colors[this.get(x, y)];
     }
-    blank(width: number, height: number) : IndexedBitmap {
-        let bitmap = new IndexedBitmap(width, height, this.bitsPerPixel);
-        bitmap.palette = this.palette;
+    blank(width?: number, height?: number, newPalette?: Palette) : IndexedBitmap {
+        let bitmap = new IndexedBitmap(width || this.width, height || this.height, newPalette || this.palette);
         return bitmap;
     }
     clone() : IndexedBitmap {
@@ -184,6 +197,7 @@ export interface BitmapAnalysis {
 }
 
 export function analyze(bitmaps: BitmapType[]) {
+    bitmaps = coerceToArray(bitmaps);
     let r = {min:{w:0,h:0}, max:{w:0,h:0}};
     for (let bmp of bitmaps) {
         if (!(bmp instanceof AbstractBitmap)) return null;
@@ -202,6 +216,7 @@ export interface MontageOptions {
 }
 
 export function montage(bitmaps: BitmapType[], options?: MontageOptions) {
+    bitmaps = coerceToArray(bitmaps);
     let minmax = (options && options.analysis) || analyze(bitmaps);
     if (minmax == null) throw new Error(`Expected an array of bitmaps`);
     let hitrects = [];
diff --git a/src/common/script/lib/io.ts b/src/common/script/lib/io.ts
index c756236a..2c1a2fe4 100644
--- a/src/common/script/lib/io.ts
+++ b/src/common/script/lib/io.ts
@@ -1,12 +1,15 @@
 
+import { FileDataCache } from "../../util";
 import { FileData, WorkingStore } from "../../workertypes";
 
 // remote resource cache
-var $$cache: WeakMap<object,FileData> = new WeakMap();
+var $$cache = new FileDataCache(); // TODO: better cache?
 // file read/write interface
 var $$store: WorkingStore;
 // backing store for data
 var $$data: {} = {};
+// module cache
+var $$modules: Map<string,{}> = new Map();
 
 export function $$setupFS(store: WorkingStore) {
     $$store = store;
@@ -38,7 +41,7 @@ export namespace data {
         return object;
     }
     export function save(object: Loadable, key: string): Loadable {
-        if ($$data && object.$$getstate) {
+        if ($$data && object && object.$$getstate) {
             $$data[key] = object.$$getstate();
         }
         return object;
@@ -67,10 +70,6 @@ export function canonicalurl(url: string) : string {
     return url;
 }
 
-export function clearcache() {
-    $$cache = new WeakMap();
-}
-
 export function fetchurl(url: string, type?: 'binary' | 'text'): FileData {
     // TODO: only works in web worker
     var xhr = new XMLHttpRequest();
@@ -99,17 +98,19 @@ export function readnocache(url: string, type?: 'binary' | 'text'): FileData {
 
 // TODO: read files too
 export function read(url: string, type?: 'binary' | 'text'): FileData {
+    // canonical-ize url
     url = canonicalurl(url);
-    // check cache
-    let cachekey = {url: url};
-    if ($$cache.has(cachekey)) {
-        return $$cache.get(cachekey);
-    }
-    let data = readnocache(url, type);
+    // check cache first
+    let cachekey = url;
+    let data = $$cache.get(cachekey);
+    if (data != null) return data;
+    // not in cache, read it
+    data = readnocache(url, type);
     if (data == null) throw new Error(`Cannot find resource "${url}"`);
     if (type === 'text' && typeof data !== 'string') throw new Error(`Resource "${url}" is not a string`);
     if (type === 'binary' && !(data instanceof Uint8Array)) throw new Error(`Resource "${url}" is not a binary file`);
-    $$cache.set(cachekey, data);
+    // store in cache
+    $$cache.put(cachekey, data);
     return data;
 }
 
@@ -129,6 +130,22 @@ export function splitlines(text: string) : string[] {
     return text.split(/\n|\r\n/g);
 }
 
+export function module(url: string) {
+    // find module in cache?
+    let key = `${url}::${url.length}`;
+    let exports = $$modules.get(key);
+    if (exports == null) {
+        let code = readnocache(url, 'text') as string;
+        let func = new Function('exports', 'module', code);
+        let module = {}; // TODO?
+        exports = {};
+        func(exports, module);
+        $$modules.set(key, exports);
+    }
+    return exports;
+}
+
+///
 
 // TODO: what if this isn't top level?
 export class Mutable<T> implements Loadable {
diff --git a/src/common/script/lib/scriptui.ts b/src/common/script/lib/scriptui.ts
index 6d256b09..9ceda395 100644
--- a/src/common/script/lib/scriptui.ts
+++ b/src/common/script/lib/scriptui.ts
@@ -1,6 +1,10 @@
 
+import { coerceToArray } from "../../util";
 import * as io from "./io";
 
+// sequence counter
+var $$seq : number = 0;
+
 // if an event is specified, it goes here
 export const EVENT_KEY = "$$event";
 
@@ -17,17 +21,22 @@ export interface InteractEvent {
     button?: boolean;
 }
 
+export type InteractCallback = (event: InteractEvent) => void;
+
 // InteractionRecord maps a target object to an interaction ID
 // the $$callback is used once per script eval, then gets nulled
 // whether or not it's invoked
 // event comes from $$data.$$event
 export class InteractionRecord implements io.Loadable {
+    readonly interacttarget: Interactive;
     interactid : number;
     lastevent : {} = null;
     constructor(
-        public readonly interacttarget: Interactive,
-        private $$callback
+        interacttarget: Interactive,
+        private $$callback: InteractCallback
     ) {
+        this.interacttarget = interacttarget || (<any>this as Interactive);
+        this.interactid = ++$$seq;
     }
     $$setstate(newstate: {interactid: number}) {
         this.interactid = newstate.interactid;
@@ -46,7 +55,7 @@ export class InteractionRecord implements io.Loadable {
         //TODO: this isn't always cleared before we serialize (e.g. if exception or move element)
         //and we do it in checkResult() too
         this.$$callback = null;
-        return this;
+        return {interactid: this.interactid};
     }
 }
 
@@ -125,17 +134,42 @@ export function select(options: any[]) {
 
 ///
 
-export class ScriptUIButtonType implements ScriptUIType {
+export class ScriptUIButtonType extends InteractionRecord implements ScriptUIType, Interactive {
     readonly uitype = 'button';
+    $$interact: InteractionRecord;
+    enabled?: boolean;
+
     constructor(
-        readonly name: string
+        readonly label: string,
+        callback: InteractCallback
     ) {
+        super(null, callback);
+        this.$$interact = this;
     }
 }
 
 export class ScriptUIButton extends ScriptUIButtonType {
 }
 
-export function button(name: string) {
-    return new ScriptUIButton(name);
+export function button(name: string, callback: InteractCallback) {
+    return new ScriptUIButton(name, callback);
+}
+
+export class ScriptUIToggle extends ScriptUIButton implements io.Loadable {
+    // share with InteractionRecord
+    $$getstate() {
+        let state = super.$$getstate() as any;
+        state.enabled = this.enabled;
+        return state;
+    }
+    $$setstate(newstate: any) {
+        this.enabled = newstate.enabled;
+        super.$$setstate(newstate);
+    }
+}
+
+export function toggle(name: string) {
+    return new ScriptUIToggle(name, function(e) {
+        this.enabled = !this.enabled;
+    });
 }
diff --git a/src/common/script/ui/notebook.ts b/src/common/script/ui/notebook.ts
index 2eb27b5c..b5cc362f 100644
--- a/src/common/script/ui/notebook.ts
+++ b/src/common/script/ui/notebook.ts
@@ -12,27 +12,27 @@ import * as scriptui from "../lib/scriptui";
 const MAX_STRING_LEN = 100;
 const DEFAULT_ASPECT = 1;
 
-interface ObjectStats {
-    type: 'prim' | 'complex' | 'bitmap'
-    width: number
-    height: number
-    units: 'em' | 'px'
-}
-
-// TODO
-class ObjectAnalyzer {
-    recurse(obj: any) : ObjectStats {
-        if (typeof obj === 'string') {
-            return { type: 'prim', width: obj.length, height: 1, units: 'em' }
-        } else if (obj instanceof Uint8Array) {
-            return { type: 'complex', width: 60, height: Math.ceil(obj.length / 16), units: 'em' }
-        } else if (typeof obj === 'object') {
-            let stats : ObjectStats = { type: 'complex', width: 0, height: 0, units: 'em'};
-            return stats; // TODO
-        } else {
-            return { type: 'prim', width: 12, height: 1, units: 'em' }
-        }
+function sendInteraction(iobj: scriptui.Interactive, type: string, event: Event, xtraprops: {}) {
+    let irec = iobj.$$interact;
+    let ievent : scriptui.InteractEvent = {interactid: irec.interactid, type, ...xtraprops};
+    if (event instanceof PointerEvent) {
+        const canvas = event.target as HTMLCanvasElement;
+        const rect = canvas.getBoundingClientRect();
+        const scaleX = canvas.width / rect.width;
+        const scaleY = canvas.height / rect.height;
+        const x = (event.clientX - rect.left) * scaleX;
+        const y = (event.clientY - rect.top) * scaleY;
+        ievent.x = Math.floor(x);
+        ievent.y = Math.floor(y);
+        // TODO: pressure, etc.
+    } else {
+        console.log("Unknown event type", event);
     }
+    // TODO: add events to queue?
+    current_project.updateDataItems([{
+        key: scriptui.EVENT_KEY,
+        value: ievent
+    }]);
 }
 
 interface ColorComponentProps {
@@ -56,27 +56,6 @@ class ColorComponent extends Component<ColorComponentProps> {
     }
 }
 
-function sendInteraction(iobj: scriptui.Interactive, type: string, event: Event, xtraprops: {}) {
-    let irec = iobj.$$interact;
-    let ievent : scriptui.InteractEvent = {interactid: irec.interactid, type, ...xtraprops};
-    if (event instanceof PointerEvent) {
-        const canvas = event.target as HTMLCanvasElement;
-        const rect = canvas.getBoundingClientRect();
-        const scaleX = canvas.width / rect.width;
-        const scaleY = canvas.height / rect.height;
-        const x = (event.clientX - rect.left) * scaleX;
-        const y = (event.clientY - rect.top) * scaleY;
-        ievent.x = Math.round(x);
-        ievent.y = Math.round(y);
-        // TODO: pressure, etc.
-    }
-    // TODO: add events to queue?
-    current_project.updateDataItems([{
-        key: scriptui.EVENT_KEY,
-        value: ievent
-    }]);
-}
-
 interface BitmapComponentProps {
     bitmap: bitmap.BitmapType;
     width: number;
@@ -253,7 +232,7 @@ function primitiveToString(obj) {
 }
 
 function isIndexedBitmap(object): object is bitmap.IndexedBitmap {
-    return object['bitsPerPixel'] && object['pixels'] && object['palette'];
+    return object['bpp'] && object['pixels'] && object['palette'];
 }
 function isRGBABitmap(object): object is bitmap.RGBABitmap {
     return object['rgba'] instanceof Uint32Array;
@@ -275,7 +254,10 @@ function objectToDiv(object: any, name: string, objpath: string): VNode<any> {
     // don't view any keys that start with "$"
     if (name && name.startsWith("$")) {
         // don't view any values that start with "$$"
-        if (name.startsWith("$$")) { return; }
+        if (name.startsWith("$$")) return;
+        // don't print if null or undefined
+        if (object == null) return;
+        // don't print key in any case
         name = null;
     }
     // TODO: limit # of items
@@ -400,9 +382,24 @@ class UISelectComponent extends Component<UIComponentProps> {
     }
 }
 
+class UIButtonComponent extends Component<UIComponentProps> {
+    render(virtualDom, containerNode, replaceNode) {
+        let button = this.props.uiobject as scriptui.ScriptUIButtonType;
+        return h('button', {
+            class: button.enabled ? 'scripting-button scripting-enabled' : 'scripting-button',
+            onClick: (e: MouseEvent) => {
+                sendInteraction(button, 'click', e, { });
+            },
+        }, [ 
+            button.label 
+        ])
+    }
+}
+
 const UI_COMPONENTS = {
     'slider': UISliderComponent,
     'select': UISelectComponent,
+    'button': UIButtonComponent,
 }
 
 ///
diff --git a/src/common/util.ts b/src/common/util.ts
index df2a5e12..47c854ab 100644
--- a/src/common/util.ts
+++ b/src/common/util.ts
@@ -1,4 +1,3 @@
-import { UintArray } from "../ide/pixeleditor";
 
 export function lpad(s:string, n:number):string {
   s += ''; // convert to string
@@ -56,7 +55,7 @@ export function toradix(v:number, nd:number, radix:number) {
   }
 }
 
-export function arrayCompare(a:any[]|UintArray, b:any[]|UintArray):boolean {
+export function arrayCompare(a:ArrayLike<any>, b:ArrayLike<any>):boolean {
   if (a == null && b == null) return true;
   if (a == null) return false;
   if (b == null) return false;
@@ -662,3 +661,34 @@ export function findIntegerFactors(x: number, mina: number, minb: number, aspect
   }
   return {a, b};
 }
+
+export class FileDataCache {
+  maxSize : number = 8000000;
+  size : number;
+  cache : Map<string, string|Uint8Array>;
+  constructor() {
+    this.reset();
+  }
+  get(key : string) : string|Uint8Array {
+    return this.cache.get(key);
+  }
+  put(key : string, value : string|Uint8Array) {
+    this.cache.set(key, value);
+    this.size += value.length;
+    if (this.size > this.maxSize) {
+      console.log('cache reset', this);
+      this.reset();
+    }
+  }
+  reset() {
+    this.cache = new Map();
+    this.size = 0;
+  }
+}
+
+export function coerceToArray<T>(arrobj: any) : T[] {
+    if (Array.isArray(arrobj)) return arrobj;
+    else if (arrobj != null && typeof arrobj[Symbol.iterator] === 'function') return Array.from(arrobj);
+    else if (typeof arrobj === 'object') return Array.from(Object.values(arrobj))
+    else throw new Error(`Expected array or object, got "${arrobj}"`);
+}
diff --git a/src/ide/ui.ts b/src/ide/ui.ts
index d306b65d..06cdf9fe 100644
--- a/src/ide/ui.ts
+++ b/src/ide/ui.ts
@@ -147,6 +147,7 @@ function fatalError(s:string) {
 }
 
 function newWorker() : Worker {
+  // TODO: return new Worker("https://8bitworkshop.com.s3-website-us-east-1.amazonaws.com/dev/gen/worker/bundle.js");
   return new Worker("./gen/worker/bundle.js");
 }
 
diff --git a/src/platform/script.ts b/src/platform/script.ts
index 3b6f751e..0664664b 100644
--- a/src/platform/script.ts
+++ b/src/platform/script.ts
@@ -1,5 +1,5 @@
 
-import { PLATFORMS, RasterVideo } from "../common/emu";
+import { PLATFORMS } from "../common/emu";
 import { Platform } from "../common/baseplatform";
 import { RunResult } from "../common/script/env";
 import { Notebook } from "../common/script/ui/notebook";