diff --git a/index.html b/index.html
index 460fff5..54ad5bc 100644
--- a/index.html
+++ b/index.html
@@ -71,6 +71,12 @@ ul.navbar li:last-child {
   background-color: rgba(255, 255, 255, 0.9);
 }
 
+.mandala-container label.checkbox {
+  display: block;
+  margin-top: 10px;
+  margin-bottom: 10px;
+}
+
 .mandala-container .color-widget {
   display: flex;
 }
diff --git a/lib/checkbox.tsx b/lib/checkbox.tsx
index 81ddb32..c43da36 100644
--- a/lib/checkbox.tsx
+++ b/lib/checkbox.tsx
@@ -8,7 +8,7 @@ type CheckboxProps = {
 
 export const Checkbox: React.FC<CheckboxProps> = (props) => {
   return (
-    <label>
+    <label className="checkbox">
       <input
         type="checkbox"
         checked={props.value}
diff --git a/lib/pages/creature-page.tsx b/lib/pages/creature-page.tsx
index b5985c8..9f5af8b 100644
--- a/lib/pages/creature-page.tsx
+++ b/lib/pages/creature-page.tsx
@@ -1,17 +1,12 @@
 import React, { useContext, useRef, useState } from "react";
 import { SvgVocabulary } from "../svg-vocabulary";
-import {
-  createSvgSymbolContext,
-  noFillIfShowingSpecs,
-  SvgSymbolData,
-} from "../svg-symbol";
+import { noFillIfShowingSpecs, SvgSymbolData } from "../svg-symbol";
 import {
   AttachmentPointType,
   ATTACHMENT_POINT_TYPES,
   iterAttachmentPoints,
 } from "../specs";
 import { Random } from "../random";
-import { SymbolContextWidget } from "../symbol-context-widget";
 import { range } from "../util";
 
 import { AutoSizingSvg } from "../auto-sizing-svg";
@@ -24,11 +19,12 @@ import {
 } from "../creature-symbol";
 import { HoverDebugHelper } from "../hover-debug-helper";
 import { svgScale, SvgTransform } from "../svg-transform";
-import { ColorWidget } from "../color-widget";
 import { NumericSlider } from "../numeric-slider";
-import { DEFAULT_BG_COLOR } from "../colors";
 import { Checkbox } from "../checkbox";
-import { createRandomColorPalette } from "../random-colors";
+import {
+  CompositionContextWidget,
+  createSvgCompositionContext,
+} from "../svg-composition-context";
 
 /** Symbols that can be the "root" (i.e., main body) of a creature. */
 const ROOT_SYMBOLS = SvgVocabulary.items.filter(
@@ -178,38 +174,26 @@ function getDownloadBasename(randomSeed: number) {
 
 export const CreaturePage: React.FC<{}> = () => {
   const svgRef = useRef<SVGSVGElement>(null);
-  const [bgColor, setBgColor] = useState(DEFAULT_BG_COLOR);
   const [randomSeed, setRandomSeed] = useState<number>(Date.now());
   const [randomlyInvert, setRandomlyInvert] = useState(true);
-  const [symbolCtx, setSymbolCtx] = useState(createSvgSymbolContext());
+  const [compCtx, setCompCtx] = useState(createSvgCompositionContext());
   const [complexity, setComplexity] = useState(INITIAL_COMPLEXITY_LEVEL);
   const defaultCtx = useContext(CreatureContext);
   const newRandomSeed = () => setRandomSeed(Date.now());
   const ctx: CreatureContextType = noFillIfShowingSpecs({
     ...defaultCtx,
-    ...symbolCtx,
+    ...compCtx,
   });
   const creature = COMPLEXITY_LEVEL_GENERATORS[complexity]({
     rng: new Random(randomSeed),
     randomlyInvert,
   });
-  const randomizeColors = () => {
-    const [bgColor, stroke, fill] = createRandomColorPalette(3);
-    setBgColor(bgColor);
-    setSymbolCtx({ ...symbolCtx, stroke, fill });
-  };
 
   return (
     <>
       <h1>Creature!</h1>
-      <SymbolContextWidget ctx={symbolCtx} onChange={setSymbolCtx}>
-        <ColorWidget label="Background" value={bgColor} onChange={setBgColor} />{" "}
-      </SymbolContextWidget>
-      <div className="thingy">
-        <button accessKey="c" onClick={randomizeColors}>
-          Randomize <u>c</u>olors!
-        </button>
-      </div>
+      <CompositionContextWidget ctx={compCtx} onChange={setCompCtx} />
+      <div className="thingy"></div>
       <div className="thingy">
         <NumericSlider
           label="Random creature complexity"
@@ -242,7 +226,7 @@ export const CreaturePage: React.FC<{}> = () => {
       </div>
       <CreatureContext.Provider value={ctx}>
         <HoverDebugHelper>
-          <AutoSizingSvg padding={20} ref={svgRef} bgColor={bgColor}>
+          <AutoSizingSvg padding={20} ref={svgRef} bgColor={compCtx.background}>
             <SvgTransform transform={svgScale(0.5)}>
               <CreatureSymbol {...creature} />
             </SvgTransform>
diff --git a/lib/pages/mandala-page.tsx b/lib/pages/mandala-page.tsx
index 411ccc0..fdbc512 100644
--- a/lib/pages/mandala-page.tsx
+++ b/lib/pages/mandala-page.tsx
@@ -1,13 +1,10 @@
 import React, { useRef, useState } from "react";
 import { AutoSizingSvg } from "../auto-sizing-svg";
 import { getBoundingBoxCenter } from "../bounding-box";
-import { ColorWidget } from "../color-widget";
-import { DEFAULT_BG_COLOR } from "../colors";
 import { ExportWidget } from "../export-svg";
 import { HoverDebugHelper } from "../hover-debug-helper";
 import { NumericSlider } from "../numeric-slider";
 import {
-  createSvgSymbolContext,
   noFillIfShowingSpecs,
   safeGetAttachmentPoint,
   SvgSymbolContent,
@@ -23,13 +20,15 @@ import {
   svgTranslate,
 } from "../svg-transform";
 import { SvgVocabulary } from "../svg-vocabulary";
-import { SymbolContextWidget } from "../symbol-context-widget";
 import { NumericRange, range } from "../util";
 import { Random } from "../random";
 import { PointWithNormal } from "../specs";
 import { getAttachmentTransforms } from "../attach";
 import { Checkbox } from "../checkbox";
-import { createRandomColorPalette } from "../random-colors";
+import {
+  CompositionContextWidget,
+  createSvgCompositionContext,
+} from "../svg-composition-context";
 
 type ExtendedMandalaCircleParams = MandalaCircleParams & {
   scaling: number;
@@ -252,10 +251,9 @@ function getRandomCircleParams(rng: Random): MandalaCircleParams {
 
 export const MandalaPage: React.FC<{}> = () => {
   const svgRef = useRef<SVGSVGElement>(null);
-  const [bgColor, setBgColor] = useState(DEFAULT_BG_COLOR);
   const [circle1, setCircle1] = useState(CIRCLE_1_DEFAULTS);
   const [circle2, setCircle2] = useState(CIRCLE_2_DEFAULTS);
-  const [baseSymbolCtx, setBaseSymbolCtx] = useState(createSvgSymbolContext());
+  const [baseCompCtx, setBaseCompCtx] = useState(createSvgCompositionContext());
   const [useTwoCircles, setUseTwoCircles] = useState(false);
   const [invertCircle2, setInvertCircle2] = useState(true);
   const [firstBehindSecond, setFirstBehindSecond] = useState(false);
@@ -265,16 +263,10 @@ export const MandalaPage: React.FC<{}> = () => {
     setCircle2({ ...circle2, ...getRandomCircleParams(rng) });
   };
 
-  const symbolCtx = noFillIfShowingSpecs(baseSymbolCtx);
+  const symbolCtx = noFillIfShowingSpecs(baseCompCtx);
 
   const circle2SymbolCtx = invertCircle2 ? swapColors(symbolCtx) : symbolCtx;
 
-  const randomizeColors = () => {
-    const [bgColor, stroke, fill] = createRandomColorPalette(3);
-    setBgColor(bgColor);
-    setBaseSymbolCtx({ ...baseSymbolCtx, stroke, fill });
-  };
-
   const circles = [
     <ExtendedMandalaCircle key="first" {...circle1} {...symbolCtx} />,
   ];
@@ -291,20 +283,15 @@ export const MandalaPage: React.FC<{}> = () => {
   return (
     <>
       <h1>Mandala!</h1>
-      <div className="mandala-container" style={{ backgroundColor: bgColor }}>
+      <div
+        className="mandala-container"
+        style={{ backgroundColor: baseCompCtx.background }}
+      >
         <div className="sidebar">
-          <SymbolContextWidget ctx={baseSymbolCtx} onChange={setBaseSymbolCtx}>
-            <ColorWidget
-              label="Background"
-              value={bgColor}
-              onChange={setBgColor}
-            />{" "}
-          </SymbolContextWidget>
-          <div className="thingy">
-            <button accessKey="c" onClick={randomizeColors}>
-              Randomize <u>c</u>olors!
-            </button>
-          </div>
+          <CompositionContextWidget
+            ctx={baseCompCtx}
+            onChange={setBaseCompCtx}
+          />
           <fieldset>
             <legend>First circle</legend>
             <ExtendedMandalaCircleParamsWidget
@@ -349,7 +336,11 @@ export const MandalaPage: React.FC<{}> = () => {
         </div>
         <div className="canvas">
           <HoverDebugHelper>
-            <AutoSizingSvg padding={20} ref={svgRef} bgColor={bgColor}>
+            <AutoSizingSvg
+              padding={20}
+              ref={svgRef}
+              bgColor={baseCompCtx.background}
+            >
               <SvgTransform transform={svgScale(0.5)}>{circles}</SvgTransform>
             </AutoSizingSvg>
           </HoverDebugHelper>
diff --git a/lib/svg-composition-context.tsx b/lib/svg-composition-context.tsx
new file mode 100644
index 0000000..68d01b4
--- /dev/null
+++ b/lib/svg-composition-context.tsx
@@ -0,0 +1,60 @@
+import React from "react";
+import { ColorWidget } from "./color-widget";
+import { DEFAULT_BG_COLOR } from "./colors";
+import { createRandomColorPalette } from "./random-colors";
+import { createSvgSymbolContext, SvgSymbolContext } from "./svg-symbol";
+import {
+  SymbolContextWidget,
+  SymbolContextWidgetProps,
+} from "./symbol-context-widget";
+
+const DEFAULT_CONTEXT: SvgCompositionContext = {
+  background: DEFAULT_BG_COLOR,
+  ...createSvgSymbolContext(),
+};
+
+export type SvgCompositionContext = SvgSymbolContext & {
+  /** The background color of the composition, as a hex hash (e.g. '#ff0000'). */
+  background: string;
+};
+
+export function createSvgCompositionContext(
+  ctx: Partial<SvgCompositionContext> = {}
+): SvgCompositionContext {
+  return {
+    ...DEFAULT_CONTEXT,
+    ...ctx,
+  };
+}
+
+export type CompositionContextWidgetProps<
+  T extends SvgCompositionContext
+> = SymbolContextWidgetProps<T>;
+
+export function CompositionContextWidget<T extends SvgCompositionContext>({
+  ctx,
+  onChange,
+  children,
+}: CompositionContextWidgetProps<T>): JSX.Element {
+  const randomizeColors = () => {
+    const [background, stroke, fill] = createRandomColorPalette(3);
+    onChange({ ...ctx, background, stroke, fill });
+  };
+
+  const extra = (
+    <button accessKey="c" onClick={randomizeColors}>
+      Randomize <u>c</u>olors!
+    </button>
+  );
+
+  return (
+    <SymbolContextWidget ctx={ctx} onChange={onChange} extraButtons={extra}>
+      {children}
+      <ColorWidget
+        label="Background"
+        value={ctx.background}
+        onChange={(background) => onChange({ ...ctx, background })}
+      />{" "}
+    </SymbolContextWidget>
+  );
+}
diff --git a/lib/svg-symbol.tsx b/lib/svg-symbol.tsx
index 0e9a4de..4373abc 100644
--- a/lib/svg-symbol.tsx
+++ b/lib/svg-symbol.tsx
@@ -30,9 +30,23 @@ export type SvgSymbolElement = (
 };
 
 export type SvgSymbolContext = {
+  /** The stroke color of the symbol, as a hex hash (e.g. '#ff0000'). */
   stroke: string;
+
+  /** The fill color of the symbol, as a hex hash (e.g. '#ff0000'). */
   fill: string;
+
+  /**
+   * Whether or not to visibly show the specifications for the symbol,
+   * e.g. its attachment points, nesting boxes, and so on.
+   */
   showSpecs: boolean;
+
+  /**
+   * Whether or not to forcibly apply a uniform stroke width to all
+   * the shapes in the symbol.  If defined, the stroke width will
+   * *not* vary as the symbol is scaled.
+   */
   uniformStrokeWidth?: number;
 };
 
@@ -43,6 +57,11 @@ const DEFAULT_CONTEXT: SvgSymbolContext = {
   uniformStrokeWidth: DEFAULT_UNIFORM_STROKE_WIDTH,
 };
 
+/**
+ * If the given symbol context is visibly showing its specifications,
+ * return one with its fill color set to "none" so that the specs can
+ * be seen more easily.
+ */
 export function noFillIfShowingSpecs<T extends SvgSymbolContext>(ctx: T): T {
   return {
     ...ctx,
@@ -50,6 +69,9 @@ export function noFillIfShowingSpecs<T extends SvgSymbolContext>(ctx: T): T {
   };
 }
 
+/**
+ * Return a symbol context with the stroke and fill colors swapped.
+ */
 export function swapColors<T extends SvgSymbolContext>(ctx: T): T {
   return {
     ...ctx,
diff --git a/lib/symbol-context-widget.tsx b/lib/symbol-context-widget.tsx
index 0bb1fac..00a4293 100644
--- a/lib/symbol-context-widget.tsx
+++ b/lib/symbol-context-widget.tsx
@@ -4,11 +4,19 @@ import { ColorWidget } from "./color-widget";
 import { NumericSlider } from "./numeric-slider";
 import { SvgSymbolContext, swapColors } from "./svg-symbol";
 
-export const SymbolContextWidget: React.FC<{
-  ctx: SvgSymbolContext;
-  onChange: (value: SvgSymbolContext) => void;
+export type SymbolContextWidgetProps<T extends SvgSymbolContext> = {
+  ctx: T;
+  onChange: (value: T) => void;
   children?: any;
-}> = ({ ctx, children, onChange }) => {
+  extraButtons?: JSX.Element;
+};
+
+export function SymbolContextWidget<T extends SvgSymbolContext>({
+  ctx,
+  children,
+  onChange,
+  extraButtons,
+}: SymbolContextWidgetProps<T>): JSX.Element {
   const updateCtx = (updates: Partial<SvgSymbolContext>) => {
     onChange({ ...ctx, ...updates });
   };
@@ -29,6 +37,7 @@ export const SymbolContextWidget: React.FC<{
       <button onClick={() => updateCtx(swapColors(ctx))}>
         Swap stroke/fill
       </button>{" "}
+      {extraButtons}
       <Checkbox
         label="Show specs"
         value={ctx.showSpecs}
@@ -48,4 +57,4 @@ export const SymbolContextWidget: React.FC<{
       )}
     </div>
   );
-};
+}