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+# Boss-Fight HUD Bar Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Gather the top of the boss fight into a themed HUD bar — back-to-menu door + "Floor N/M · <domain>" on the left, icon-only SFX/BGM on the right — and move the boss name just beneath it.
+
+**Architecture:** A new `src/ui/bossHud.ts` exposes two pure, unit-tested helpers (`darken`, `formatRunLabel`) and a Phaser composer `mountBossHud(scene, opts)` that draws the bar and reuses the existing `mountMenuButton` (door) and `mountAudioToggles` (now with an `iconOnly` option). `BossFightScene.create()` swaps its separate door/audio mounts for one `mountBossHud(...)` call.
+
+**Tech Stack:** TypeScript, Phaser 3, Vite, Vitest, Biome. Paths/commands relative to `public/dungeon/` unless noted.
+
+**Source spec:** `docs/superpowers/specs/2026-05-30-boss-fight-hud-design.md`.
+
+---
+
+## Working directory & conventions
+
+- Run `npx vitest` / `npx tsc` / `npm run dev` from `public/dungeon/`.
+- **Lint:** the Biome binary lives in the **repo-root** node_modules. Lint changed files with
+  `/Users/Daniel_Sallai/dev/ai-kb/node_modules/.bin/biome check --write <files>` (NOT
+  `npx @biomejs/biome`, which pulls an incompatible 2.x). The CI command is `npm run lint`
+  from the repo root `/Users/Daniel_Sallai/dev/ai-kb`. A prior PR went red purely on Biome
+  formatting — never skip the lint step.
+- Canvas is 960×720 (center x=480). The boss has `environmentColor` (hex int) and — after
+  Task 2 — `domainShort`.
+
+## File Structure
+
+- **Create** `src/ui/bossHud.ts` — `darken`, `formatRunLabel` (Task 1), `mountBossHud` (Task 5).
+- **Create** `src/ui/bossHud.test.ts` — unit tests for the pure helpers + a `domainShort` guard.
+- **Modify** `src/types.ts` — add `domainShort` to `BossDefinition` (Task 2).
+- **Modify** `src/config.ts` — add `domainShort` to each boss (Task 2).
+- **Modify** `src/ui/audioToggles.ts` — `iconOnly` + `y` options (Task 3).
+- **Modify** `src/ui/inFightNav.ts` — `mountMenuButton` optional position (Task 4).
+- **Modify** `src/scenes/BossFightScene.ts` — mount the HUD; move the boss name (Task 6).
+
+---
+
+## Task 1: Pure helpers — `darken` + `formatRunLabel`
+
+**Files:**
+- Create: `src/ui/bossHud.ts`
+- Test: `src/ui/bossHud.test.ts`
+
+- [ ] **Step 1: Write the failing test**
+
+Create `src/ui/bossHud.test.ts`:
+
+```typescript
+import { describe, expect, it } from 'vitest';
+import { darken, formatRunLabel } from './bossHud';
+
+describe('darken', () => {
+  it('multiplies each channel and rounds', () => {
+    // 0x4e=78 → 39 (0x27); 0x1b=27 → 14 (0x0e)
+    expect(darken(0x4e4e1b, 0.5)).toBe(0x27270e);
+  });
+  it('factor 0 yields black', () => {
+    expect(darken(0x4e4e1b, 0)).toBe(0x000000);
+  });
+  it('clamps channels at 255', () => {
+    expect(darken(0xffffff, 2)).toBe(0xffffff);
+  });
+});
+
+describe('formatRunLabel', () => {
+  it('shows floor (1-indexed) / total and domain when a campaign exists', () => {
+    const campaign = { floorsCleared: 0, bossOrder: ['a', 'b', 'c', 'd', 'e'] };
+    expect(formatRunLabel(campaign, 'MCP')).toBe('Floor 1/5 · MCP');
+  });
+  it('uses the later floor number as the run advances', () => {
+    const campaign = { floorsCleared: 3, bossOrder: ['a', 'b', 'c', 'd', 'e'] };
+    expect(formatRunLabel(campaign, 'Context')).toBe('Floor 4/5 · Context');
+  });
+  it('falls back to just the domain when there is no campaign (debug/isolated)', () => {
+    expect(formatRunLabel(undefined, 'MCP')).toBe('MCP');
+  });
+});
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `npx vitest run src/ui/bossHud.test.ts`
+Expected: FAIL — module/exports missing.
+
+- [ ] **Step 3: Implement the helpers**
+
+Create `src/ui/bossHud.ts`:
+
+```typescript
+/**
+ * Multiply each RGB channel of a hex color by `factor` (clamped to 0–255).
+ * factor < 1 darkens; used to derive the HUD bar shade from a boss's
+ * environmentColor.
+ */
+export function darken(color: number, factor: number): number {
+  const clamp = (v: number) => Math.max(0, Math.min(255, Math.round(v)));
+  const r = clamp(((color >> 16) & 0xff) * factor);
+  const g = clamp(((color >> 8) & 0xff) * factor);
+  const b = clamp((color & 0xff) * factor);
+  return (r << 16) | (g << 8) | b;
+}
+
+/**
+ * Left-side HUD run label. With a campaign: "Floor <n>/<total> · <domain>"
+ * (n is 1-indexed). Without one (isolated/debug fight): just the domain.
+ */
+export function formatRunLabel(
+  campaign: { floorsCleared: number; bossOrder: string[] } | undefined,
+  domainShort: string,
+): string {
+  if (!campaign) return domainShort;
+  return `Floor ${campaign.floorsCleared + 1}/${campaign.bossOrder.length} · ${domainShort}`;
+}
+```
+
+- [ ] **Step 4: Run test to verify it passes**
+
+Run: `npx vitest run src/ui/bossHud.test.ts`
+Expected: PASS (6 tests).
+
+- [ ] **Step 5: Lint + commit**
+
+```bash
+/Users/Daniel_Sallai/dev/ai-kb/node_modules/.bin/biome check --write src/ui/bossHud.ts src/ui/bossHud.test.ts
+git add src/ui/bossHud.ts src/ui/bossHud.test.ts
+git commit -m "feat(dungeon): darken + formatRunLabel helpers for boss HUD"
+```
+
+---
+
+## Task 2: `domainShort` on every boss
+
+**Files:**
+- Modify: `src/types.ts` (the `BossDefinition` interface)
+- Modify: `src/config.ts` (each of the 5 `BOSSES`)
+- Test: `src/ui/bossHud.test.ts` (append a guard)
+
+- [ ] **Step 1: Write the failing guard test**
+
+Append to `src/ui/bossHud.test.ts` (add `BOSSES` to a new import line at the top):
+
+```typescript
+import { BOSSES } from '../config';
+
+describe('boss domainShort', () => {
+  it('every boss declares a non-empty domainShort', () => {
+    for (const b of BOSSES) {
+      expect(b.domainShort.length).toBeGreaterThan(0);
+    }
+  });
+});
+```
+
+- [ ] **Step 2: Run it — expect a TYPE/compile failure**
+
+Run: `npx tsc --noEmit`
+Expected: FAIL — `Property 'domainShort' does not exist on type 'BossDefinition'`.
+
+- [ ] **Step 3: Add the field to the type**
+
+In `src/types.ts`, add `domainShort` to `BossDefinition` (right after `domain`):
+
+```typescript
+export interface BossDefinition {
+  id: string;
+  name: string;
+  domain: string;
+  domainShort: string;
+  theme: string;
+  taunts: { correct: string[]; wrong: string[] };
+  environmentColor: number; // hex for Phaser fillRect, etc.
+}
+```
+
+- [ ] **Step 4: Add the value to each boss**
+
+In `src/config.ts`, add a `domainShort` line immediately after the `domain:` line of each boss:
+
+- `the-orchestrator` (`domain-1-agentic`): `    domainShort: 'Agentic',`
+- `the-compiler-king` (`domain-2-claude-code`): `    domainShort: 'Claude Code',`
+- `the-grammarian` (`domain-3-prompt-engineering`): `    domainShort: 'Prompting',`
+- `the-tool-smith` (`domain-4-mcp`): `    domainShort: 'MCP',`
+- `the-memory-kraken` (`domain-5-context`): `    domainShort: 'Context',`
+
+- [ ] **Step 5: Verify type + test pass**
+
+Run: `npx tsc --noEmit && npx vitest run src/ui/bossHud.test.ts`
+Expected: `tsc` clean; tests PASS (now 7).
+
+- [ ] **Step 6: Lint + commit**
+
+```bash
+/Users/Daniel_Sallai/dev/ai-kb/node_modules/.bin/biome check --write src/types.ts src/config.ts src/ui/bossHud.test.ts
+git add src/types.ts src/config.ts src/ui/bossHud.test.ts
+git commit -m "feat(dungeon): add domainShort to every boss"
+```
+
+---
+
+## Task 3: `iconOnly` option on the audio toggles
+
+**Files:**
+- Modify: `src/ui/audioToggles.ts`
+
+No unit test: `audioToggles` is Phaser + localStorage + registry coupled and currently
+untested by design; the change is a rendering option verified manually (Task 6) and exercised
+through `mountBossHud`. Keep the change minimal.
+
+- [ ] **Step 1: Extend `MountOptions`**
+
+In `src/ui/audioToggles.ts`, change the `MountOptions` interface to:
+
+```typescript
+interface MountOptions {
+  onBgmToggle?: (muted: boolean) => void;
+  /** Render glyph-only buttons (no "BGM"/"SFX" text), vertically centered. */
+  iconOnly?: boolean;
+  /** Vertical anchor for the buttons. Defaults to 18 (top-right corner). */
+  y?: number;
+}
+```
+
+- [ ] **Step 2: Honor the options in the mount body**
+
+Inside `mountAudioToggles`, replace the `makeButton` definition, the two `*Label` functions,
+and the two `makeButton(...)` calls (the block from `const makeButton = (x: number, ...` down
+to `const sfx = makeButton(855, sfxLabel);`) with:
+
+```typescript
+  const iconOnly = opts.iconOnly === true;
+  const y = opts.y ?? 18;
+
+  const makeButton = (x: number, label: () => string): Phaser.GameObjects.Text => {
+    const t = scene.add.text(x, y, label(), {
+      fontSize: '14px',
+      color: '#c0c0d0',
+      fontFamily: 'monospace',
+      backgroundColor: '#1a1a2a',
+      padding: { x: iconOnly ? 5 : 8, y: 4 },
+    });
+    t.setOrigin(1, iconOnly ? 0.5 : 0);
+    t.setInteractive({ useHandCursor: true });
+    t.setScrollFactor(0);
+    t.setDepth(1000);
+    return t;
+  };
+
+  // '🔇' = 🔇 (muted), '🎵' = 🎵 (BGM), '🔊' = 🔊 (SFX).
+  const label = (icon: string, name: string, muted: boolean): string => {
+    const glyph = muted ? '🔇' : icon;
+    return iconOnly ? glyph : `${glyph} ${name}`;
+  };
+  const bgmLabel = (): string => label('🎵', 'BGM', bgmMuted());
+  const sfxLabel = (): string => label('🔊', 'SFX', sfxMuted());
+
+  const bgm = makeButton(iconOnly ? 938 : 935, bgmLabel);
+  const sfx = makeButton(iconOnly ? 904 : 855, sfxLabel);
+```
+
+(The rest of the function — the `bgm.on(...)`/`sfx.on(...)` handlers and the `return { bgm, sfx }` — is unchanged. The handlers already call `setText(bgmLabel())` / `setText(sfxLabel())`, so they pick up the icon-only labels automatically.)
+
+- [ ] **Step 3: Verify nothing broke**
+
+Run: `npx vitest run && npx tsc --noEmit`
+Expected: all green (Hub still mounts the labeled version since it passes no `iconOnly`).
+
+- [ ] **Step 4: Lint + commit**
+
+```bash
+/Users/Daniel_Sallai/dev/ai-kb/node_modules/.bin/biome check --write src/ui/audioToggles.ts
+git add src/ui/audioToggles.ts
+git commit -m "feat(dungeon): icon-only option for audio toggles"
+```
+
+---
+
+## Task 4: Optional position for `mountMenuButton`
+
+**Files:**
+- Modify: `src/ui/inFightNav.ts`
+
+- [ ] **Step 1: Add the optional position parameter**
+
+In `src/ui/inFightNav.ts`, change the `mountMenuButton` signature and the `scene.add.image`
+call so the door position is configurable (defaulting to today's `28,28`):
+
+```typescript
+export function mountMenuButton(
+  scene: Phaser.Scene,
+  onExit: () => void,
+  position: { x: number; y: number } = { x: 28, y: 28 },
+): void {
+  const door = scene.add
+    .image(position.x, position.y, 'td-tiles', DOOR_FRAME)
+    .setScale(2)
+    .setDepth(1000)
+    .setInteractive({ useHandCursor: true });
+
+  door.on('pointerover', () => door.setTint(0xffe070));
+  door.on('pointerout', () => door.clearTint());
+  door.on('pointerdown', onExit);
+}
+```
+
+- [ ] **Step 2: Verify the existing test still passes**
+
+Run: `npx vitest run src/ui/inFightNav.test.ts`
+Expected: PASS — the existing test calls `mountMenuButton(scene, onExit)` (no position), so the default is used; the scene fake ignores coordinates.
+
+- [ ] **Step 3: Lint + commit**
+
+```bash
+/Users/Daniel_Sallai/dev/ai-kb/node_modules/.bin/biome check --write src/ui/inFightNav.ts
+git add src/ui/inFightNav.ts
+git commit -m "feat(dungeon): mountMenuButton accepts an optional position"
+```
+
+---
+
+## Task 5: `mountBossHud` composer
+
+**Files:**
+- Modify: `src/ui/bossHud.ts` (append the composer + its imports)
+
+No new unit test: this is Phaser scene wiring (draws rects, delegates to `mountMenuButton` /
+`mountAudioToggles`). Its pure inputs (`darken`, `formatRunLabel`) are covered in Task 1; the
+composed result is verified manually in Task 6.
+
+- [ ] **Step 1: Add imports at the top of `src/ui/bossHud.ts`**
+
+Add above the existing `darken` export:
+
+```typescript
+import type Phaser from 'phaser';
+import type { BossDefinition } from '../types';
+import { mountAudioToggles } from './audioToggles';
+import { mountMenuButton } from './inFightNav';
+
+const BAR_HEIGHT = 44;
+const BAR_DARKEN = 0.5; // bar fill = boss color × this; bottom border is lighter
+```
+
+- [ ] **Step 2: Append the composer at the end of `src/ui/bossHud.ts`**
+
+```typescript
+export interface BossHudOptions {
+  boss: BossDefinition;
+  campaign: { floorsCleared: number; bossOrder: string[] } | undefined;
+  onExit: () => void;
+  onBgmToggle: (muted: boolean) => void;
+}
+
+/**
+ * Mount the boss-fight HUD: a themed top bar (darkened boss color) holding the
+ * back-to-menu door + "Floor N/M · <domain>" on the left and icon-only
+ * SFX/BGM on the right. Reuses mountMenuButton + mountAudioToggles so their
+ * behavior/persistence is unchanged.
+ */
+export function mountBossHud(scene: Phaser.Scene, opts: BossHudOptions): void {
+  const { boss, campaign, onExit, onBgmToggle } = opts;
+  const midY = BAR_HEIGHT / 2;
+
+  // Themed bar fill + a slightly lighter bottom border so it frames cleanly.
+  scene.add
+    .rectangle(480, midY, 960, BAR_HEIGHT, darken(boss.environmentColor, BAR_DARKEN))
+    .setDepth(900);
+  scene.add
+    .rectangle(480, BAR_HEIGHT - 1, 960, 2, darken(boss.environmentColor, 0.9))
+    .setDepth(901);
+
+  // Left: door + run label.
+  mountMenuButton(scene, onExit, { x: 28, y: midY });
+  scene.add
+    .text(64, midY, formatRunLabel(campaign, boss.domainShort), {
+      fontSize: '14px',
+      color: '#f5e4b3',
+      fontFamily: 'monospace',
+    })
+    .setOrigin(0, 0.5)
+    .setDepth(1000);
+
+  // Right: icon-only SFX/BGM, vertically centered in the bar.
+  mountAudioToggles(scene, { iconOnly: true, y: midY, onBgmToggle });
+}
+```
+
+- [ ] **Step 3: Verify build + types + tests**
+
+Run: `npx vitest run && npx tsc --noEmit && npm run build 2>&1 | grep -E "built in|error"`
+Expected: all tests pass, `tsc` clean, build succeeds.
+
+- [ ] **Step 4: Lint + commit**
+
+```bash
+/Users/Daniel_Sallai/dev/ai-kb/node_modules/.bin/biome check --write src/ui/bossHud.ts
+git add src/ui/bossHud.ts
+git commit -m "feat(dungeon): mountBossHud composer (bar + door + run label + audio)"
+```
+
+---
+
+## Task 6: Wire the HUD into the boss fight + verify
+
+**Files:**
+- Modify: `src/scenes/BossFightScene.ts`
+
+- [ ] **Step 1: Fix the imports**
+
+In `src/scenes/BossFightScene.ts`:
+- Change line 28 from `import { REGISTRY_BGM_MUTED, mountAudioToggles } from '../ui/audioToggles';` to `import { REGISTRY_BGM_MUTED } from '../ui/audioToggles';` (keep `REGISTRY_BGM_MUTED` — it's still used at the BGM-start guard ~line 398; drop `mountAudioToggles`).
+- Delete the line `import { mountMenuButton } from '../ui/inFightNav';`.
+- Add `import { mountBossHud } from '../ui/bossHud';` among the `../ui/*` imports.
+
+- [ ] **Step 2: Move the boss name below the bar**
+
+Find the "Boss name at top center" block and change the y from `30` to `66`:
+
+```typescript
+    // Boss name — sits just below the HUD bar (bar occupies y 0–44).
+    this.add
+      .text(480, 66, this.boss.name, {
+        fontSize: '24px',
+        color: '#f5e4b3',
+        fontFamily: 'monospace',
+      })
+      .setOrigin(0.5);
+```
+
+- [ ] **Step 3: Replace the two mounts with `mountBossHud`**
+
+Replace the whole block from the `// Mute toggles (top-right).` comment through the
+`mountMenuButton(this, () => this.exitToHub());` line (the `mountAudioToggles(this, {...});`
+call and the `// Back-to-menu control …` comment + `mountMenuButton(...)` call) with:
+
+```typescript
+    // Top HUD bar: themed strip with the back-to-menu door + "Floor N/M ·
+    // <domain>" on the left and icon-only SFX/BGM on the right. onBgmToggle
+    // starts/stops our procedural BGM; SFX mute flows through Phaser's sound
+    // manager automatically.
+    mountBossHud(this, {
+      boss: this.boss,
+      campaign: this.registry.get('campaign') as Campaign | undefined,
+      onExit: () => this.exitToHub(),
+      onBgmToggle: (muted) => {
+        if (muted) this.bgm.stop();
+        else this.bgm.start(this.boss.id, this.sound as unknown as { context?: AudioContext });
+      },
+    });
+```
+
+(`Campaign` is already imported in this file: `import type { Campaign } from '../game/dungeon';`.)
+
+- [ ] **Step 4: Verify build + types + full suite**
+
+Run: `npx vitest run && npx tsc --noEmit && npm run build 2>&1 | grep -E "built in|error"`
+Expected: all green. `tsc` must show no unused-import error for `mountAudioToggles`/`mountMenuButton` (both removed from this file).
+
+- [ ] **Step 5: CI-parity lint (repo root)**
+
+Run (from `/Users/Daniel_Sallai/dev/ai-kb`): `npm run lint`
+Expected: `Checked N files … No fixes applied.`, exit 0. If anything flags, run `npm run lint:fix`, re-verify, and amend.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add src/scenes/BossFightScene.ts
+git commit -m "feat(dungeon): mount boss HUD bar; move boss name below it"
+```
+
+- [ ] **Step 7: Manual verification in the browser**
+
+Run `npm run dev`, open the URL, start a real run, enter a boss fight, and confirm:
+- A bar spans the top in a darker, boss-themed tone with a subtle bottom border.
+- Left: the door, then `Floor 1/5 · <domain>` (correct floor number and domain short).
+- Right: SFX + BGM as **icons only**; clicking each still mutes and the state persists across a reload.
+- The boss name sits just below the bar, not overlapping it or the question bubble.
+- Advance a floor (beat a boss) → the floor number increments on the next fight.
+- A `?demo` run shows the bar/label correctly; a debug-isolated boss preview shows just the domain (no "Floor") and doesn't crash.
+- Check ≥2 different bosses for color cohesion (e.g. Tool-Smith vs Memory-Kraken). If the bar reads too dark/muddy, bump `BAR_DARKEN` in `bossHud.ts` (one number) and re-check.
+
+- [ ] **Step 8: No commit** (verification only). Record the manual result in the PR description.
+
+---
+
+## Self-review notes (for the implementer)
+
+- Tasks 1–4 are prerequisites for Task 5 (`mountBossHud` uses `darken`, `formatRunLabel`,
+  `boss.domainShort`, the audio `iconOnly` option, and the door position arg). Do them in order.
+- Depths: bar `900`, border `901`, all interactive contents `1000` — keep the door/label/audio
+  above the bar.
+- Don't reintroduce a `mountAudioToggles` or `mountMenuButton` call directly in
+  `BossFightScene` — they're composed inside `mountBossHud` now. But keep the
+  `REGISTRY_BGM_MUTED` import (BGM-start guard still uses it).
+- Pixel positions (x=64 label, x=904/938 audio, y=66 boss name) are starting values; nudge
+  them during Step 7 if spacing looks off — they don't affect tests.
diff --git a/docs/superpowers/specs/2026-05-30-boss-fight-hud-design.md b/docs/superpowers/specs/2026-05-30-boss-fight-hud-design.md
new file mode 100644
index 0000000..7e26b86
--- /dev/null
+++ b/docs/superpowers/specs/2026-05-30-boss-fight-hud-design.md
@@ -0,0 +1,142 @@
+# Boss-Fight HUD Bar — design
+
+**Date:** 2026-05-30
+**Status:** draft — awaiting user review
+**Context:** Slay the Cert dungeon game (`public/dungeon/`).
+
+## Problem
+
+The top of the boss fight is a loose scatter: the boss name floats at y=30, the
+back-to-menu door sits free at (28,28), and the audio toggles float top-right as
+text+emoji buttons. There's no run context (which floor, which domain). This feature
+gathers the top into a single **HUD bar** — a themed strip holding the door, run progress,
+and audio controls — and moves the boss name just beneath it.
+
+Canvas is 960×720 (center x=480).
+
+## Design
+
+### The bar
+
+A full-width strip across the top: a rectangle `(480, 22)` sized `960×44`, filled with a
+**darkened shade of the active boss's `environmentColor`** (RGB × ~0.5), plus a subtle 2px
+bottom border (a slightly lighter shade) at y≈43 so it frames rather than distracts. The
+bar renders at depth 900; all its contents at depth 1000. Per-boss this reads as a cohesive
+extension of the scene (Tool-Smith forge `0x4e4e1b`, Memory-Kraken depths `0x1b2d4e`, etc.).
+
+### Left cluster
+
+- **Door** — the existing `mountMenuButton`, unchanged in behavior, nudged to the bar's
+  vertical center (~`(28, 22)`). `mountMenuButton` gains an optional `{ x, y }` position
+  (defaulting to today's `28,28`) so the HUD can place it.
+- **Run label** — `Floor 1/5 · MCP` at ~`(64, 22)`, origin `(0, 0.5)`, monospace, parchment
+  tone (`#f5e4b3`). Floor = `floorsCleared + 1` / `bossOrder.length`. In isolated/debug
+  fights there is no campaign, so the label gracefully drops the floor part and shows just
+  the domain short (e.g. `MCP`).
+
+### Right cluster
+
+The **same** audio toggles, **icon-only**. `mountAudioToggles` gains an `iconOnly?: boolean`
+(and a `y?` anchor) option: when set, the buttons render just the glyph (🎵/🔇 for BGM,
+🔊/🔇 for SFX) with no "BGM"/"SFX" text, right-aligned inside the bar (~`bgm x=938`,
+`sfx x=904`, vertically centered). All mute-state, registry, `sound.mute` sync, persistence,
+and `onBgmToggle` logic is reused unchanged — the Hub keeps its labeled version (no
+`iconOnly`).
+
+### Boss name
+
+Moves from `(480, 30)` to just below the bar at ~`(480, 66)`, same 24px parchment style,
+still centered above the question bubble (bubble body starts ~y=130).
+
+### Structure
+
+A new `src/ui/bossHud.ts` exporting `mountBossHud(scene, opts)` composes the whole strip:
+the bar rect + border, `mountMenuButton` (door), the run label, and `mountAudioToggles`
+(icon-only). `BossFightScene.create()` replaces its separate `mountMenuButton` and
+`mountAudioToggles` calls with a single `mountBossHud(...)`, and moves the boss-name text
+down.
+
+```
+mountBossHud(scene, {
+  boss,            // BossDefinition — for environmentColor + domainShort
+  campaign,        // Campaign | undefined (from registry) — for the floor label
+  onExit,          // () => void  → BossFightScene.exitToHub
+  onBgmToggle,     // (muted: boolean) => void  → start/stop ProceduralBGM
+}): void
+```
+
+### Pure seams (unit-tested)
+
+Two pure helpers fall out and are unit-tested (no Phaser):
+
+- `darken(color: number, factor: number): number` — channel-wise multiply with 0–255 clamp.
+  Lives in `bossHud.ts`.
+  ```ts
+  export function darken(color: number, factor: number): number {
+    const clamp = (v: number) => Math.max(0, Math.min(255, Math.round(v)));
+    const r = clamp(((color >> 16) & 0xff) * factor);
+    const g = clamp(((color >> 8) & 0xff) * factor);
+    const b = clamp((color & 0xff) * factor);
+    return (r << 16) | (g << 8) | b;
+  }
+  ```
+- `formatRunLabel(campaign, domainShort): string` — the with/without-campaign branch.
+  ```ts
+  export function formatRunLabel(
+    campaign: { floorsCleared: number; bossOrder: string[] } | undefined,
+    domainShort: string,
+  ): string {
+    if (!campaign) return domainShort;
+    return `Floor ${campaign.floorsCleared + 1}/${campaign.bossOrder.length} · ${domainShort}`;
+  }
+  ```
+
+### Data: `domainShort`
+
+Add `domainShort: string` to the `BossDefinition` interface (`src/types.ts`) and to each of
+the five bosses in `src/config.ts`:
+
+| boss | domain | domainShort |
+|---|---|---|
+| the-orchestrator | domain-1-agentic | `Agentic` |
+| the-compiler-king | domain-2-claude-code | `Claude Code` |
+| the-grammarian | domain-3-prompt-engineering | `Prompting` |
+| the-tool-smith | domain-4-mcp | `MCP` |
+| the-memory-kraken | domain-5-context | `Context` |
+
+## Scope / non-goals
+
+- **In:** the HUD bar (themed strip), run label (floor + domain short), icon-only audio
+  reuse, boss-name reposition, `domainShort` data, the `bossHud.ts` composer, and the two
+  pure helpers.
+- **Out:** hero/boss HP readouts (they stay where they are, near the sprites); a settings
+  menu; any change to audio behavior or persistence; animating the bar; touching the Hub's
+  audio toggles.
+
+## Files touched
+
+- **Create** `src/ui/bossHud.ts` — `mountBossHud`, `darken`, `formatRunLabel`.
+- **Create** `src/ui/bossHud.test.ts` — unit tests for `darken` + `formatRunLabel`.
+- **Modify** `src/ui/audioToggles.ts` — add `iconOnly?: boolean` + `y?: number` options.
+- **Modify** `src/ui/inFightNav.ts` — `mountMenuButton` accepts optional `{ x, y }`.
+- **Modify** `src/types.ts` — `domainShort` on `BossDefinition`.
+- **Modify** `src/config.ts` — `domainShort` on each boss.
+- **Modify** `src/scenes/BossFightScene.ts` — call `mountBossHud(...)` (replacing the
+  separate door + audio mounts); move the boss-name text below the bar.
+
+## Testing
+
+- **Unit:** `darken` (e.g. `darken(0x4e4e1b, 0.5) === 0x27270e`; clamps; `factor 0` → black)
+  and `formatRunLabel` (with a 5-boss campaign at floor 0 → `"Floor 1/5 · MCP"`; `undefined`
+  campaign → `"MCP"`).
+- **Unit (light):** `mountMenuButton`'s existing click test still passes with the new
+  optional position arg.
+- **Manual:** in a real run, the bar spans the top in a darker boss-themed tone; door +
+  `Floor N/5 · <domain>` on the left, icon-only SFX/BGM on the right (toggles still mute and
+  persist); boss name sits just below the bar; no overlap with the question bubble. Check a
+  couple of bosses for color cohesion, and a `?demo`/debug-isolated fight for the no-floor
+  fallback. Tune final pixel positions against the running dev server.
+
+## Branch / merge plan
+
+Standalone feature on `feat/boss-hud` off `main`. Its own PR.
diff --git a/public/dungeon/src/config.ts b/public/dungeon/src/config.ts
index 1634498..3c93341 100644
--- a/public/dungeon/src/config.ts
+++ b/public/dungeon/src/config.ts
@@ -36,6 +36,7 @@ export const BOSSES: BossDefinition[] = [
     id: 'the-orchestrator',
     name: 'The Orchestrator',
     domain: 'domain-1-agentic',
+    domainShort: 'Agentic',
     theme: 'Throne hall with chess-piece attendants',
     taunts: {
       correct: [
@@ -51,6 +52,7 @@ export const BOSSES: BossDefinition[] = [
     id: 'the-compiler-king',
     name: 'The Compiler-King',
     domain: 'domain-2-claude-code',
+    domainShort: 'Claude Code',
     theme: 'Iron workshop; command sigils',
     taunts: {
       correct: ['Your config compiles.', 'The build succeeds.', 'Compilation: 0 errors.'],
@@ -62,6 +64,7 @@ export const BOSSES: BossDefinition[] = [
     id: 'the-grammarian',
     name: 'The Grammarian',
     domain: 'domain-3-prompt-engineering',
+    domainShort: 'Prompting',
     theme: 'Library of carved stone scrolls',
     taunts: {
       correct: ['Precise.', 'Your tags are sacred.', 'Structure holds.'],
@@ -73,6 +76,7 @@ export const BOSSES: BossDefinition[] = [
     id: 'the-tool-smith',
     name: 'The Tool-Smith',
     domain: 'domain-4-mcp',
+    domainShort: 'MCP',
     theme: 'Forge surrounded by schemas-as-runes',
     taunts: {
       correct: ['The schema holds.', 'Well-forged.', 'Your tools cut true.'],
@@ -84,6 +88,7 @@ export const BOSSES: BossDefinition[] = [
     id: 'the-memory-kraken',
     name: 'The Memory-Kraken',
     domain: 'domain-5-context',
+    domainShort: 'Context',
     theme: 'Flooded archive; sinking context-shelves',
     taunts: {
       correct: ['You remember.', 'The tide holds.', 'Context preserved.'],
diff --git a/public/dungeon/src/scenes/BossFightScene.ts b/public/dungeon/src/scenes/BossFightScene.ts
index adc8c46..7d27c01 100644
--- a/public/dungeon/src/scenes/BossFightScene.ts
+++ b/public/dungeon/src/scenes/BossFightScene.ts
@@ -25,9 +25,9 @@ import type {
   SessionLog,
   SpellId,
 } from '../types';
-import { REGISTRY_BGM_MUTED, mountAudioToggles } from '../ui/audioToggles';
+import { REGISTRY_BGM_MUTED } from '../ui/audioToggles';
+import { mountBossHud } from '../ui/bossHud';
 import { attachRectHover, attachTextHover } from '../ui/buttonHover';
-import { mountMenuButton } from '../ui/inFightNav';
 import { NarratorDispatcher } from '../ui/narrator/NarratorDispatcher';
 import { NarratorOverlay } from '../ui/narrator/NarratorOverlay';
 import { LinePool } from '../ui/narrator/linePool';
@@ -194,14 +194,9 @@ export class BossFightScene extends Phaser.Scene {
     // before everything else so it sits at the bottom of the z-stack.
     renderBackdrop(this, this.boss.id);
 
-    // Boss name at top center
-    this.add
-      .text(480, 30, this.boss.name, {
-        fontSize: '24px',
-        color: '#f5e4b3',
-        fontFamily: 'monospace',
-      })
-      .setOrigin(0.5);
+    // (Boss name now lives centered in the top HUD bar — see mountBossHud.
+    // The old top-center banner floated on the brick wall and clipped the top
+    // of the question scroll.)
 
     // --- Speech bubble (question area) ---
     // Filled rectangle body
@@ -241,12 +236,12 @@ export class BossFightScene extends Phaser.Scene {
       .setOrigin(0.5, 0);
 
     // --- Hero sprite (left) ---
-    this.heroSprite = this.add.image(120, 330, 'hero').setScale(3);
+    this.heroSprite = this.add.image(85, 330, 'hero').setScale(3);
 
     // Hero HP hearts below sprite. Slightly smaller than before so the
     // label stack under the hero is a compact 2-line group.
     this.heroHpText = this.add
-      .text(120, 405, '', {
+      .text(85, 405, '', {
         fontSize: '12px',
         color: '#8bc34a',
         fontFamily: 'monospace',
@@ -256,7 +251,7 @@ export class BossFightScene extends Phaser.Scene {
     // Hero name label \u2014 intentionally tiny so it reads as a subtitle
     // rather than competing with the HP text above it.
     this.add
-      .text(120, 420, 'WARLOCK', {
+      .text(85, 420, 'WARLOCK', {
         fontSize: '9px',
         color: '#808090',
         fontFamily: 'monospace',
@@ -266,12 +261,19 @@ export class BossFightScene extends Phaser.Scene {
     // --- Boss sprite (right) ---
     const bossKey = `boss-${this.boss.id}`;
     const bossTexKey = this.textures.exists(bossKey) ? bossKey : 'hero';
-    this.bossSprite = this.add.image(840, 330, bossTexKey).setScale(4);
+    // Boss is scaled up (6 vs hero's 3) for presence; y nudged up so its feet
+    // ground on the same floor line as the hero rather than sinking lower.
+    this.bossSprite = this.add.image(875, 306, bossTexKey).setScale(6);
+
+    // (Boss name now lives centered in the top HUD bar — see mountBossHud /
+    // bossHud.ts. The bar is a themed strip above the brick wall and question
+    // scroll, so the name clips neither; a side/overhead plate in the scene
+    // body caught the near-full-width scroll's corner.)
 
     // Boss HP hearts below boss sprite \u2014 match the hero HP scale so both
     // sides read as symmetric status lines.
     this.bossHpText = this.add
-      .text(840, 405, '', {
+      .text(875, 405, '', {
         fontSize: '12px',
         color: '#ff6b6b',
         fontFamily: 'monospace',
@@ -280,12 +282,12 @@ export class BossFightScene extends Phaser.Scene {
 
     // Taunt text below boss
     this.tauntText = this.add
-      .text(840, 450, '', {
+      .text(875, 450, '', {
         fontSize: '12px',
         color: '#d0c090',
         fontFamily: 'monospace',
         fontStyle: 'italic',
-        wordWrap: { width: 260 },
+        wordWrap: { width: 160 },
         align: 'center',
       })
       .setOrigin(0.5, 0);
@@ -401,21 +403,21 @@ export class BossFightScene extends Phaser.Scene {
     this.events.once('shutdown', () => this.bgm.stop());
     this.events.once('destroy', () => this.bgm.stop());
 
-    // Mute toggles (top-right). onBgmToggle starts/stops our procedural
-    // BGM as the user flips the control; SFX mute flows through Phaser's
-    // sound manager automatically.
-    mountAudioToggles(this, {
+    // Top HUD bar: themed strip with the back-to-menu door + "Floor N/M ·
+    // <domain>" on the left and icon-only SFX/BGM on the right. onBgmToggle
+    // starts/stops our procedural BGM; SFX mute flows through Phaser's sound
+    // manager automatically.
+    mountBossHud(this, {
+      boss: this.boss,
+      bossName: this.boss.name,
+      campaign: this.registry.get('campaign') as Campaign | undefined,
+      onExit: () => this.exitToHub(),
       onBgmToggle: (muted) => {
         if (muted) this.bgm.stop();
         else this.bgm.start(this.boss.id, this.sound as unknown as { context?: AudioContext });
       },
     });
 
-    // Back-to-menu control (top-left). Leaving flushes a resumable mid-fight
-    // save, so the Hub offers "Continue (… mid-fight)". No-op save for
-    // isolated/demo runs — those just abandon the throwaway fight.
-    mountMenuButton(this, () => this.exitToHub());
-
     // Install Feel Pack — hit-stop, shake grading, squash-stretch, stagger-back, ambient dust.
     installFeelPack(this, { heroSprite: this.heroSprite, bossSprite: this.bossSprite });
 
diff --git a/public/dungeon/src/types.ts b/public/dungeon/src/types.ts
index f8dfd36..e16e4e5 100644
--- a/public/dungeon/src/types.ts
+++ b/public/dungeon/src/types.ts
@@ -37,10 +37,14 @@ export interface Bank {
 }
 
 // Boss types
+// Short display label for a domain, paired 1:1 with `domain`. Closed set of 5.
+export type DomainShort = 'Agentic' | 'Claude Code' | 'Prompting' | 'MCP' | 'Context';
+
 export interface BossDefinition {
   id: string;
   name: string;
   domain: string;
+  domainShort: DomainShort;
   theme: string;
   taunts: { correct: string[]; wrong: string[] };
   environmentColor: number; // hex for Phaser fillRect, etc.
diff --git a/public/dungeon/src/ui/audioToggles.ts b/public/dungeon/src/ui/audioToggles.ts
index 6eb46f1..468afa4 100644
--- a/public/dungeon/src/ui/audioToggles.ts
+++ b/public/dungeon/src/ui/audioToggles.ts
@@ -43,6 +43,13 @@ function savePreference(key: string, muted: boolean): void {
 
 interface MountOptions {
   onBgmToggle?: (muted: boolean) => void;
+  /**
+   * Render glyph-only buttons (no "BGM"/"SFX" text), vertically centered and
+   * right-anchored tighter for a compact HUD bar (changes layout, not just text).
+   */
+  iconOnly?: boolean;
+  /** Vertical anchor for the buttons. Defaults to 18 (top-right corner). */
+  y?: number;
 }
 
 /**
@@ -73,26 +80,34 @@ export function mountAudioToggles(
   // subsequent play() calls respect it.
   scene.sound.mute = sfxMuted();
 
+  const iconOnly = opts.iconOnly === true;
+  const y = opts.y ?? 18;
+
   const makeButton = (x: number, label: () => string): Phaser.GameObjects.Text => {
-    const t = scene.add.text(x, 18, label(), {
+    const t = scene.add.text(x, y, label(), {
       fontSize: '14px',
       color: '#c0c0d0',
       fontFamily: 'monospace',
       backgroundColor: '#1a1a2a',
-      padding: { x: 8, y: 4 },
+      padding: { x: iconOnly ? 5 : 8, y: 4 },
     });
-    t.setOrigin(1, 0);
+    t.setOrigin(1, iconOnly ? 0.5 : 0);
     t.setInteractive({ useHandCursor: true });
     t.setScrollFactor(0);
     t.setDepth(1000);
     return t;
   };
 
-  const bgmLabel = (): string => (bgmMuted() ? '\uD83D\uDD07 BGM' : '\uD83C\uDFB5 BGM');
-  const sfxLabel = (): string => (sfxMuted() ? '\uD83D\uDD07 SFX' : '\uD83D\uDD0A SFX');
+  // '\uD83D\uDD07' = \uD83D\uDD07 muted; '\uD83C\uDFB5' = \uD83C\uDFB5 BGM; '\uD83D\uDD0A' = \uD83D\uDD0A SFX.
+  const label = (icon: string, name: string, muted: boolean): string => {
+    const glyph = muted ? '\uD83D\uDD07' : icon;
+    return iconOnly ? glyph : `${glyph} ${name}`;
+  };
+  const bgmLabel = (): string => label('\uD83C\uDFB5', 'BGM', bgmMuted());
+  const sfxLabel = (): string => label('\uD83D\uDD0A', 'SFX', sfxMuted());
 
-  const bgm = makeButton(935, bgmLabel);
-  const sfx = makeButton(855, sfxLabel);
+  const bgm = makeButton(iconOnly ? 938 : 935, bgmLabel);
+  const sfx = makeButton(iconOnly ? 904 : 855, sfxLabel);
 
   bgm.on('pointerdown', () => {
     const next = !bgmMuted();
diff --git a/public/dungeon/src/ui/bossHud.test.ts b/public/dungeon/src/ui/bossHud.test.ts
new file mode 100644
index 0000000..0240f9c
--- /dev/null
+++ b/public/dungeon/src/ui/bossHud.test.ts
@@ -0,0 +1,38 @@
+import { describe, expect, it } from 'vitest';
+import { BOSSES } from '../config';
+import { darken, formatRunLabel } from './bossHud';
+
+describe('darken', () => {
+  it('multiplies each channel and rounds', () => {
+    // 0x4e=78 → 39 (0x27); 0x1b=27 → 14 (0x0e)
+    expect(darken(0x4e4e1b, 0.5)).toBe(0x27270e);
+  });
+  it('factor 0 yields black', () => {
+    expect(darken(0x4e4e1b, 0)).toBe(0x000000);
+  });
+  it('clamps channels at 255', () => {
+    expect(darken(0xffffff, 2)).toBe(0xffffff);
+  });
+});
+
+describe('formatRunLabel', () => {
+  it('shows floor (1-indexed) / total and domain when a campaign exists', () => {
+    const campaign = { floorsCleared: 0, bossOrder: ['a', 'b', 'c', 'd', 'e'] };
+    expect(formatRunLabel(campaign, 'MCP')).toBe('Floor 1/5 · MCP');
+  });
+  it('uses the later floor number as the run advances', () => {
+    const campaign = { floorsCleared: 3, bossOrder: ['a', 'b', 'c', 'd', 'e'] };
+    expect(formatRunLabel(campaign, 'Context')).toBe('Floor 4/5 · Context');
+  });
+  it('falls back to just the domain when there is no campaign (debug/isolated)', () => {
+    expect(formatRunLabel(undefined, 'MCP')).toBe('MCP');
+  });
+});
+
+describe('boss domainShort', () => {
+  it('every boss declares a non-empty domainShort', () => {
+    for (const b of BOSSES) {
+      expect(b.domainShort.length).toBeGreaterThan(0);
+    }
+  });
+});
diff --git a/public/dungeon/src/ui/bossHud.ts b/public/dungeon/src/ui/bossHud.ts
new file mode 100644
index 0000000..cf72dd0
--- /dev/null
+++ b/public/dungeon/src/ui/bossHud.ts
@@ -0,0 +1,93 @@
+import type Phaser from 'phaser';
+import type { Campaign } from '../game/dungeon';
+import type { BossDefinition } from '../types';
+import { mountAudioToggles } from './audioToggles';
+import { mountMenuButton } from './inFightNav';
+
+const BAR_HEIGHT = 44;
+const BAR_DARKEN = 0.5; // bar fill = boss color × this factor (darker)
+const BAR_BORDER_DARKEN = 0.9; // bottom border = boss color × this; lighter than the fill
+
+// The only Campaign fields the HUD needs. A type-only Pick keeps this UI module
+// decoupled from game logic while still breaking if those fields ever rename.
+type CampaignRunInfo = Pick<Campaign, 'floorsCleared' | 'bossOrder'>;
+
+/**
+ * Multiply each RGB channel of a hex color by `factor` (clamped to 0–255).
+ * factor < 1 darkens; used to derive the HUD bar shade from a boss's
+ * environmentColor.
+ */
+export function darken(color: number, factor: number): number {
+  const clamp = (v: number) => Math.max(0, Math.min(255, Math.round(v)));
+  const r = clamp(((color >> 16) & 0xff) * factor);
+  const g = clamp(((color >> 8) & 0xff) * factor);
+  const b = clamp((color & 0xff) * factor);
+  return (r << 16) | (g << 8) | b;
+}
+
+/**
+ * Left-side HUD run label. With a campaign: "Floor <n>/<total> · <domain>"
+ * (n is 1-indexed). Without one (isolated/debug fight): just the domain.
+ */
+export function formatRunLabel(campaign: CampaignRunInfo | undefined, domainShort: string): string {
+  if (!campaign) return domainShort;
+  return `Floor ${campaign.floorsCleared + 1}/${campaign.bossOrder.length} · ${domainShort}`;
+}
+
+export interface BossHudOptions {
+  boss: BossDefinition;
+  campaign: CampaignRunInfo | undefined;
+  onExit: () => void;
+  onBgmToggle: (muted: boolean) => void;
+  /** Boss name, rendered centered in the bar. Sitting on the themed strip
+   *  keeps it clear of the brick wall and the near-full-width question scroll
+   *  below, which a scene-body plate would clip. */
+  bossName?: string;
+}
+
+/**
+ * Mount the boss-fight HUD: a themed top bar (darkened boss color) holding the
+ * back-to-menu door + "Floor N/M · <domain>" on the left and icon-only
+ * SFX/BGM on the right. Reuses mountMenuButton + mountAudioToggles so their
+ * behavior/persistence is unchanged.
+ */
+export function mountBossHud(scene: Phaser.Scene, opts: BossHudOptions): void {
+  const { boss, campaign, onExit, onBgmToggle, bossName } = opts;
+  const midY = BAR_HEIGHT / 2;
+
+  // Themed bar fill + a slightly lighter bottom border so it frames cleanly.
+  scene.add
+    .rectangle(480, midY, 960, BAR_HEIGHT, darken(boss.environmentColor, BAR_DARKEN))
+    .setDepth(900);
+  scene.add
+    .rectangle(480, BAR_HEIGHT - 1, 960, 2, darken(boss.environmentColor, BAR_BORDER_DARKEN))
+    .setDepth(901);
+
+  // Left: door + run label.
+  mountMenuButton(scene, onExit, { x: 28, y: midY });
+  scene.add
+    .text(64, midY, formatRunLabel(campaign, boss.domainShort), {
+      fontSize: '14px',
+      color: '#f5e4b3',
+      fontFamily: 'monospace',
+    })
+    .setOrigin(0, 0.5)
+    .setDepth(1000);
+
+  // Center: boss name, in amber (brand accent). Centered between the left run
+  // label and the right audio cluster, on the themed strip — clears both the
+  // brick wall and the question scroll that side/overhead plates would clip.
+  if (bossName) {
+    scene.add
+      .text(480, midY, bossName, {
+        fontSize: '18px',
+        color: '#ffca28',
+        fontFamily: 'monospace',
+      })
+      .setOrigin(0.5)
+      .setDepth(1000);
+  }
+
+  // Right: icon-only SFX/BGM, vertically centered in the bar.
+  mountAudioToggles(scene, { iconOnly: true, y: midY, onBgmToggle });
+}
diff --git a/public/dungeon/src/ui/inFightNav.ts b/public/dungeon/src/ui/inFightNav.ts
index 9971516..05b21ed 100644
--- a/public/dungeon/src/ui/inFightNav.ts
+++ b/public/dungeon/src/ui/inFightNav.ts
@@ -4,13 +4,18 @@ import type Phaser from 'phaser';
 const DOOR_FRAME = 45;
 
 /**
- * Mount a small door icon in the top-left of a boss fight that acts as a
- * back-to-menu control. Clicking it invokes onExit. Visuals only — the caller
- * decides what leaving does (see BossFightScene.exitToHub).
+ * Mount a small door icon that acts as a back-to-menu control (default
+ * top-left; the caller may reposition via `position` — the HUD bar centers it).
+ * Clicking it invokes onExit. Visuals only — the caller decides what leaving
+ * does (see BossFightScene.exitToHub).
  */
-export function mountMenuButton(scene: Phaser.Scene, onExit: () => void): void {
+export function mountMenuButton(
+  scene: Phaser.Scene,
+  onExit: () => void,
+  position: { x: number; y: number } = { x: 28, y: 28 },
+): void {
   const door = scene.add
-    .image(28, 28, 'td-tiles', DOOR_FRAME)
+    .image(position.x, position.y, 'td-tiles', DOOR_FRAME)
     .setScale(2)
     .setDepth(1000)
     .setInteractive({ useHandCursor: true });