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+# Day Counter + 2x Indicator Implementation Plan
+
+> **For Claude:** REQUIRED SUB-SKILL: Use superpowers:executing-plans to implement this plan task-by-task.
+
+**Goal:** Add a "Day N" counter to the left of the day/night indicator and double the indicator's size.
+
+**Architecture:** Server computes `dayNumber` centrally in GameLoop, broadcasts it in StateUpdate. Client TimeIndicator renders it. Existing inline day calculation in inventionSystem replaced with centralized method.
+
+**Tech Stack:** TypeScript, Socket.io, HTML/CSS DOM (TimeIndicator), shared types
+
+---
+
+### Task 1: Add `dayNumber` to StateUpdate type
+
+**Files:**
+- Modify: `shared/src/types.ts:178-182`
+
+**Step 1: Add dayNumber field to StateUpdate**
+
+In `shared/src/types.ts`, add `dayNumber` to the `StateUpdate` interface:
+
+```typescript
+export interface StateUpdate {
+  entities: EntityState[];
+  tick: number;
+  gameTime: number; // 0.0-1.0 normalized position in day/night cycle
+  dayNumber: number; // 1-indexed day counter
+}
+```
+
+**Step 2: Rebuild shared types**
+
+Run: `npx -w shared tsc`
+Expected: Clean compile, no errors
+
+**Step 3: Commit**
+
+```bash
+git add shared/src/types.ts
+git commit -m "feat: add dayNumber to StateUpdate type"
+```
+
+---
+
+### Task 2: Add getCycleTicks() and getDayNumber() to GameLoop
+
+**Files:**
+- Modify: `server/src/game/GameLoop.ts:342-347`
+
+**Step 1: Add getCycleTicks() private helper and getDayNumber() method**
+
+Replace the existing `getGameTime()` method and add new methods after it in `server/src/game/GameLoop.ts`:
+
+```typescript
+  private getCycleTicks(): number {
+    const dayTicks = 100 / this.runtimeConstants.get('ENERGY_DECAY_PER_TICK');
+    const nightTicks = dayTicks / this.runtimeConstants.get('DAY_NIGHT_RATIO');
+    return Math.round(dayTicks + nightTicks);
+  }
+
+  getGameTime(): number {
+    const cycleTicks = this.getCycleTicks();
+    return (this.tick % cycleTicks) / cycleTicks;
+  }
+
+  getDayNumber(): number {
+    return Math.floor(this.tick / this.getCycleTicks()) + 1;
+  }
+```
+
+**Step 2: Verify server compiles**
+
+Run: `npx -w server tsc --noEmit`
+Expected: Clean compile
+
+**Step 3: Commit**
+
+```bash
+git add server/src/game/GameLoop.ts
+git commit -m "feat: add getCycleTicks() and getDayNumber() to GameLoop"
+```
+
+---
+
+### Task 3: Include dayNumber in state broadcast
+
+**Files:**
+- Modify: `server/src/network/stateSerializer.ts:100-102`
+- Modify: `server/src/network/SocketServer.ts:36`
+
+**Step 1: Update serializeStateUpdate to accept and include dayNumber**
+
+In `server/src/network/stateSerializer.ts`, change the function signature and return value:
+
+```typescript
+export function serializeStateUpdate(world: World, tick: number, gameTime: number, dayNumber: number): StateUpdate {
+  const entities = world.query('position').map(id => serializeEntity(world, id));
+  return { entities, tick, gameTime, dayNumber };
+}
+```
+
+**Step 2: Update SocketServer broadcast call**
+
+In `server/src/network/SocketServer.ts` line 36, add `getDayNumber()`:
+
+```typescript
+const update = serializeStateUpdate(this.gameLoop.world, this.gameLoop.getTick(), this.gameLoop.getGameTime(), this.gameLoop.getDayNumber());
+```
+
+**Step 3: Verify server compiles**
+
+Run: `npx -w server tsc --noEmit`
+Expected: Clean compile
+
+**Step 4: Commit**
+
+```bash
+git add server/src/network/stateSerializer.ts server/src/network/SocketServer.ts
+git commit -m "feat: broadcast dayNumber in state updates"
+```
+
+---
+
+### Task 4: Replace inline day calculation in inventionSystem
+
+**Files:**
+- Modify: `server/src/systems/inventionSystem.ts:14,21-26,148-152`
+
+**Step 1: Pass getDayNumber callback into createInventionSystem**
+
+Change the factory function signature to accept a `getDayNumber` callback:
+
+```typescript
+export function createInventionSystem(
+  llmService: LlmService,
+  narrationService: NarrationService,
+  eventMemoryService: EventMemoryService,
+  onInventionCreated?: (summary: InventionSummary) => void,
+  getDayNumber?: () => number,
+): InventionSystem {
+```
+
+**Step 2: Replace inline day calculation**
+
+Replace lines 148-152 (the inline day calculation):
+
+```typescript
+          // Compute current day
+          const dayTicks = 100 / ENERGY_DECAY_PER_TICK;
+          const nightTicks = dayTicks / DAY_NIGHT_RATIO;
+          const cycleTicks = Math.round(dayTicks + nightTicks);
+          const day = Math.floor(tick / cycleTicks) + 1;
+```
+
+With:
+
+```typescript
+          const day = getDayNumber ? getDayNumber() : 1;
+```
+
+**Step 3: Remove unused imports**
+
+Remove `ENERGY_DECAY_PER_TICK` and `DAY_NIGHT_RATIO` from the import on line 14 (if no longer used elsewhere in file):
+
+```typescript
+// Remove this line:
+import { ENERGY_DECAY_PER_TICK, DAY_NIGHT_RATIO } from '@dflike/shared';
+```
+
+**Step 4: Update GameLoop to pass getDayNumber**
+
+In `server/src/game/GameLoop.ts` around line 75, update the `createInventionSystem` call:
+
+```typescript
+    this.inventionSystem = createInventionSystem(
+      this.llmService,
+      this.narrationService,
+      this.eventMemoryService,
+      (summary) => this.onInventionCreated?.(summary),
+      () => this.getDayNumber(),
+    );
+```
+
+**Step 5: Run tests**
+
+Run: `npm -w server run test`
+Expected: All 408 tests pass
+
+**Step 6: Commit**
+
+```bash
+git add server/src/systems/inventionSystem.ts server/src/game/GameLoop.ts
+git commit -m "refactor: use centralized getDayNumber() in inventionSystem"
+```
+
+---
+
+### Task 5: Double TimeIndicator dimensions and add day counter
+
+**Files:**
+- Modify: `client/src/ui/TimeIndicator.ts` (full file)
+
+**Step 1: Add dayLabel field and update constructor**
+
+Add a `dayLabel` property and a new DOM element for it. Update all dimensions to 2x. The full updated constructor and fields:
+
+Add new field:
+```typescript
+  private dayLabel: HTMLDivElement;
+  private lastDayNumber = 0;
+```
+
+In the constructor, update these CSS values:
+- Container gap: `5px` → `10px`
+- Sun icon font-size: `10px` → `20px`, text-shadow blur `4px` → `8px`
+- Track height: `8px` → `16px`, border: `2px` → `4px`, box-shadow blur `6px` → `12px`
+- Day section width: `dayFraction * 120` → `dayFraction * 240`
+- Divider width: `1px` → `2px`
+- Night section width: `(1 - dayFraction) * 120` → `(1 - dayFraction) * 240`
+- Marker width: `3px` → `6px`, top: `-1px` → `-2px`, height calc: `calc(100% + 2px)` → `calc(100% + 4px)`, box-shadow blur `4px` → `8px`
+- Moon icon font-size: `9px` → `18px`, text-shadow blur `4px` → `8px`
+
+Add day label element before appending children:
+
+```typescript
+    // Day counter label
+    this.dayLabel = document.createElement('div');
+    this.dayLabel.style.cssText = `
+      font-size: 10px;
+      color: #e0d0b0;
+      text-shadow: 0 0 4px #00000088;
+      line-height: 1;
+      white-space: nowrap;
+    `;
+    this.dayLabel.textContent = 'Day 1';
+```
+
+Update container children order — day label first:
+
+```typescript
+    this.container.appendChild(this.dayLabel);
+    this.container.appendChild(this.sunIcon);
+    this.container.appendChild(track);
+    this.container.appendChild(this.moonIcon);
+```
+
+**Step 2: Update the update() method**
+
+Change signature to accept dayNumber and update the track width constant:
+
+```typescript
+  update(gameTime: number, dayNumber: number): void {
+    // Update day label when day changes
+    if (dayNumber !== this.lastDayNumber) {
+      this.lastDayNumber = dayNumber;
+      this.dayLabel.textContent = `Day ${dayNumber}`;
+    }
+
+    const key = Math.round(gameTime * 200).toString();
+    if (key === this.lastTimeKey) return;
+    this.lastTimeKey = key;
+
+    const totalWidth = 240 + 2; // 240px sections + 2px divider
+    const px = gameTime * totalWidth;
+    // ... rest unchanged
+```
+
+**Step 3: Commit**
+
+```bash
+git add client/src/ui/TimeIndicator.ts
+git commit -m "feat: double TimeIndicator size and add day counter"
+```
+
+---
+
+### Task 6: Pass dayNumber from GameScene to TimeIndicator
+
+**Files:**
+- Modify: `client/src/scenes/GameScene.ts`
+
+**Step 1: Add dayNumber tracking field**
+
+Find where `targetGameTime` and `currentGameTime` are declared and add:
+
+```typescript
+  private currentDayNumber = 1;
+```
+
+**Step 2: Store dayNumber from state updates**
+
+In `handleStateUpdate()` (around line 674-675), add:
+
+```typescript
+  private handleStateUpdate(update: StateUpdate): void {
+    this.targetGameTime = update.gameTime;
+    this.currentDayNumber = update.dayNumber;
+```
+
+**Step 3: Pass dayNumber to TimeIndicator.update()**
+
+In the `update()` method (around line 799), change:
+
+```typescript
+    this.timeIndicator.update(this.currentGameTime, this.currentDayNumber);
+```
+
+**Step 4: Verify client builds**
+
+Run: `npm -w client run build`
+Expected: Clean build
+
+**Step 5: Commit**
+
+```bash
+git add client/src/scenes/GameScene.ts
+git commit -m "feat: pass dayNumber from state updates to TimeIndicator"
+```
+
+---
+
+### Task 7: Manual verification
+
+**Step 1: Start server and client**
+
+Run server: `npm -w server run dev`
+Run client: `npm -w client run dev`
+
+**Step 2: Verify in browser**
+
+- Day/night indicator should be approximately 2x larger
+- "Day N" text should appear to the left of the sun icon
+- Day counter should increment when the day/night cycle completes
+- Marker should still move smoothly across the track
+
+**Step 3: Run all server tests**
+
+Run: `npm -w server run test`
+Expected: All tests pass