diff --git a/CLAUDE.md b/CLAUDE.md
index cde8c1f..e770f57 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -20,6 +20,7 @@ Reusable single-screen SceneryStack template. Run `npm run rename` to fork it to
 | `src/sim-screen/view/SimScreenSummaryContent.ts` | Accessible screen summary (reference a11y pattern) |
 | `src/sim-screen/view/SimKeyboardHelpContent.ts` | Keyboard-help dialog content |
 | `src/common/SimPanel.ts` | Pre-themed `Panel` wrapper (uses `SimColors` automatically) |
+| `src/common/SimButtonOptions.ts` | Flat button-appearance option bundles + light-control-surface combo-box options |
 | `src/common/TimeModel.ts` | Composable play/pause + elapsed-time model for animated sims |
 | `scripts/generate-icons.ts` | PNG icons from `public/icons/icon.svg` |
 | `scripts/rename-sim.ts` | Automated fork/rename across all files and folders |
@@ -58,6 +59,30 @@ export class FrictionModel implements TModel {
 Wire the view to `TimeControlNode` from `scenerystack/scenery-phet` binding on
 `model.timer.isPlayingProperty`.
 
+### SimButtonOptions
+
+SceneryStack's push/round buttons default to a 3-D/beveled look; every button in the sim
+should be flat instead. Spread these into the relevant options object:
+
+```typescript
+import { FLAT_RESET_ALL_BUTTON_OPTIONS, FLAT_RECTANGULAR_BUTTON_OPTIONS } from "../../common/SimButtonOptions.js";
+
+const resetAllButton = new ResetAllButton({ ...FLAT_RESET_ALL_BUTTON_OPTIONS, listener: () => {...} });
+const exampleButton = new RectangularPushButton({ ...FLAT_RECTANGULAR_BUTTON_OPTIONS, content, listener });
+```
+
+`FLAT_PLAY_PAUSE_STEP_BUTTON_OPTIONS` spreads into `TimeControlNode`'s `playPauseStepButtonOptions`;
+`TIME_CONTROL_SPEED_RADIO_OPTIONS` fixes `TimeControlNode`'s speed-radio label color, which
+otherwise defaults to black text on the sim's dark default-mode panels. `SIM_COMBO_BOX_OPTIONS`
+themes a `ComboBox`'s button/list chrome to the light control surface below; pair item labels
+with `LIGHT_SURFACE_TEXT_FILL` (not `SimColors.textColorProperty`, which is for panel-fill text).
+
+`SimColors.ts` backs this with a "light control surfaces" section —
+`controlSurfaceColorProperty`, `controlSurfaceDisabledColorProperty`,
+`controlSurfaceTextColorProperty` — identical white/dark-text values in both default and
+projector profiles, so any component that must stay light regardless of theme (combo boxes,
+flat buttons, editable fields) keeps readable contrast automatically.
+
 ## Accessibility
 
 This template is the **canonical accessibility reference** for OpenPhysics sims. It ships with
diff --git a/src/SimColors.ts b/src/SimColors.ts
index 803af54..3c30ad6 100644
--- a/src/SimColors.ts
+++ b/src/SimColors.ts
@@ -71,6 +71,29 @@ const SimColors = {
     default: "#e0e0e0",
     projector: "#1a1a1a",
   }),
+
+  // ── Light control surfaces ───────────────────────────────────────────────────
+  // White chrome (combo boxes, flat push buttons, editable input fields) stays light
+  // in both profiles; its text stays dark. Same values in default and projector mode,
+  // but defined here so every color lives in one themeable place.
+
+  /** Fill of light control surfaces: combo-box button/list, editable input fields. */
+  controlSurfaceColorProperty: new ProfileColorProperty(SimNamespace, "controlSurface", {
+    default: "#ffffff",
+    projector: "#ffffff",
+  }),
+
+  /** Fill of a disabled control surface (grayed-out editable input field). */
+  controlSurfaceDisabledColorProperty: new ProfileColorProperty(SimNamespace, "controlSurfaceDisabled", {
+    default: "#cccccc",
+    projector: "#cccccc",
+  }),
+
+  /** Text on light control surfaces: combo items, flat-button labels, field values, preferences. */
+  controlSurfaceTextColorProperty: new ProfileColorProperty(SimNamespace, "controlSurfaceText", {
+    default: "#1a1a1a",
+    projector: "#1a1a1a",
+  }),
 };
 
 export default SimColors;
diff --git a/src/common/SimButtonOptions.ts b/src/common/SimButtonOptions.ts
new file mode 100644
index 0000000..adcce51
--- /dev/null
+++ b/src/common/SimButtonOptions.ts
@@ -0,0 +1,52 @@
+/**
+ * SimButtonOptions.ts
+ *
+ * Shared flat button appearance for the sim. Rectangular and round push buttons
+ * default to SceneryStack's 3-D appearance; pass these options (or spread them
+ * into nested button options) for a flat look everywhere.
+ */
+
+import type { PlayPauseStepButtonGroupOptions, TimeControlNodeOptions } from "scenerystack/scenery-phet";
+import { ButtonNode, type ComboBoxOptions } from "scenerystack/sun";
+import SimColors from "../SimColors.js";
+
+export const FLAT_BUTTON_APPEARANCE_OPTIONS = {
+  buttonAppearanceStrategy: ButtonNode.FlatAppearanceStrategy,
+} as const;
+
+/** Text on flat push buttons and combo-box items (always on a light control surface). */
+export const LIGHT_SURFACE_TEXT_FILL = SimColors.controlSurfaceTextColorProperty;
+
+/**
+ * Combo-box chrome for panels. Item labels must use {@link LIGHT_SURFACE_TEXT_FILL}, not
+ * {@link SimColors.textColorProperty} — that color is for labels on the dark panel fill.
+ */
+export const SIM_COMBO_BOX_OPTIONS = {
+  buttonFill: SimColors.controlSurfaceColorProperty,
+  listFill: SimColors.controlSurfaceColorProperty,
+  buttonStroke: SimColors.panelBorderColorProperty,
+  listStroke: SimColors.panelBorderColorProperty,
+} satisfies Pick<ComboBoxOptions, "buttonFill" | "listFill" | "buttonStroke" | "listStroke">;
+
+/** Options for RectangularPushButton and NumberControl arrow buttons. */
+export const FLAT_RECTANGULAR_BUTTON_OPTIONS = FLAT_BUTTON_APPEARANCE_OPTIONS;
+
+/** Options for ResetAllButton (extends RoundPushButton). */
+export const FLAT_RESET_ALL_BUTTON_OPTIONS = FLAT_BUTTON_APPEARANCE_OPTIONS;
+
+/** Nested options for TimeControlNode play / pause / step round buttons. */
+export const FLAT_PLAY_PAUSE_STEP_BUTTON_OPTIONS = {
+  playPauseButtonOptions: FLAT_BUTTON_APPEARANCE_OPTIONS,
+  stepForwardButtonOptions: FLAT_BUTTON_APPEARANCE_OPTIONS,
+  stepBackwardButtonOptions: FLAT_BUTTON_APPEARANCE_OPTIONS,
+} satisfies PlayPauseStepButtonGroupOptions;
+
+/**
+ * Speed radio labels for TimeControlNode. SceneryStack Text defaults to black, which
+ * is low-contrast on the sim's dark Default-mode panels.
+ */
+export const TIME_CONTROL_SPEED_RADIO_OPTIONS = {
+  speedRadioButtonGroupOptions: {
+    labelOptions: { fill: SimColors.textColorProperty },
+  },
+} satisfies Pick<TimeControlNodeOptions, "speedRadioButtonGroupOptions">;
diff --git a/src/sim-screen/view/SimScreenView.ts b/src/sim-screen/view/SimScreenView.ts
index 8c8bb54..a6c191b 100644
--- a/src/sim-screen/view/SimScreenView.ts
+++ b/src/sim-screen/view/SimScreenView.ts
@@ -24,6 +24,7 @@ import { Node, Rectangle, Text } from "scenerystack/scenery";
 import { ResetAllButton } from "scenerystack/scenery-phet";
 import type { ScreenViewOptions } from "scenerystack/sim";
 import { ScreenView } from "scenerystack/sim";
+import { FLAT_RESET_ALL_BUTTON_OPTIONS } from "../../common/SimButtonOptions.js";
 import SimColors from "../../SimColors.js";
 import { SCREEN_VIEW_MARGIN } from "../../SimConstants.js";
 import type { SimModel } from "../model/SimModel.js";
@@ -67,6 +68,7 @@ export class SimScreenView extends ScreenView {
     //
     //   const a11y = StringManager.getInstance().getA11yStrings();
     //   const exampleButton = new RectangularPushButton({
+    //     ...FLAT_RECTANGULAR_BUTTON_OPTIONS, // flat appearance, not SceneryStack's default 3-D look
     //     content: someIcon,
     //     listener: () => model.doSomething(),
     //     accessibleName: a11y.controls.exampleControlStringProperty,
@@ -76,6 +78,7 @@ export class SimScreenView extends ScreenView {
     // ── Reset All button ──────────────────────────────────────────────────────
     // Always position at bottom-right (PhET convention).
     const resetAllButton = new ResetAllButton({
+      ...FLAT_RESET_ALL_BUTTON_OPTIONS,
       listener: () => {
         model.reset();
         this.reset();