docs: complete Epic 1 review, create story 2.1 best score tracking

Epic 1 code review passed with 0 patches needed — all 6 stories
marked done. 6 deferred items logged for Epics 2-5. Created story
2-1-best-score-tracking as ready-for-dev to begin Epic 2.

bmad/_bmad-output/implementation-artifacts/1-1-project-scaffold-and-dev-environment.md

@@ -1,6 +1,6 @@
 # Story 1.1: Project Scaffold & Dev Environment
 
-Status: review
+Status: done
 
 ## Story
 

bmad/_bmad-output/implementation-artifacts/1-2-game-logic-module.md

@@ -1,6 +1,6 @@
 # Story 1.2: Game Logic Module
 
-Status: review
+Status: done
 
 ## Story
 

bmad/_bmad-output/implementation-artifacts/1-3-game-board-and-tile-rendering.md

@@ -1,6 +1,6 @@
 # Story 1.3: Game Board & Tile Rendering
 
-Status: review
+Status: done
 
 ## Story
 

bmad/_bmad-output/implementation-artifacts/2-1-best-score-tracking.md

@@ -0,0 +1,105 @@
+# Story 2.1: Best Score Tracking
+
+Status: ready-for-dev
+
+## Story
+
+As a player,
+I want to see my best score alongside my current score,
+so that I have a motivational anchor and can track my all-time progress.
+
+## Acceptance Criteria
+
+1. When the current score exceeds the best score after a merge, the best score display updates immediately to match the current score
+2. When the player starts a new game, the best score remains unchanged (it persists across games within the session)
+
+## Tasks / Subtasks
+
+- [ ] Task 1: Add bestScore state to App.svelte (AC: #1, #2)
+  - [ ] Add `let bestScore = $state(0);` as a new reactive state variable
+  - [ ] Add `$effect` that watches `gameState.score` — when it exceeds `bestScore`, update `bestScore`
+  - [ ] Replace hardcoded `bestScore={0}` with `bestScore={bestScore}` in the ScoreBoard prop
+
+- [ ] Task 2: Preserve bestScore across New Game (AC: #2)
+  - [ ] Verify that `handleNewGame()` resets `gameState` via `initGame()` but does NOT reset `bestScore`
+  - [ ] `bestScore` is a separate `$state` variable, not part of `gameState` — it survives `initGame()` by design
+
+- [ ] Task 3: Verify existing tests still pass
+  - [ ] Run `npx vitest run` — all 38 existing tests must pass (no game-logic.js changes)
+
+## Dev Notes
+
+### Architecture Compliance
+
+- **State ownership:** `bestScore` lives in `App.svelte` as a `$state` rune — NOT inside the game state object
+- **Props-down pattern:** `App.svelte` passes `bestScore` to `ScoreBoard` via prop (already wired, just hardcoded to 0)
+- **No game-logic.js changes:** Best score is a UI/session concern, not game logic. The game-logic module stays pure.
+- **No storage.js yet:** localStorage persistence is Story 2.2. This story is in-memory only — best score resets on page refresh.
+
+### Critical Anti-Patterns (DO NOT)
+
+- DO NOT add `bestScore` to the `gameState` object — it is NOT part of the canonical game state shape `{ grid, score, won, keepPlaying }`
+- DO NOT create a `storage.js` module yet — that is Story 2.2
+- DO NOT use `$derived` for bestScore — it needs to be a `$state` that persists across game resets (derived would reset when gameState resets)
+- DO NOT use Svelte stores (`writable`, `readable`) — this project uses Svelte 5 runes only
+
+### Implementation Pattern
+
+The correct pattern uses `$effect` to watch score changes:
+
+```javascript
+let bestScore = $state(0);
+
+$effect(() => {
+  if (gameState.score > bestScore) {
+    bestScore = gameState.score;
+  }
+});
+```
+
+This works because:
+- `$effect` runs whenever `gameState.score` changes (reactive dependency)
+- `bestScore` is a separate `$state`, so `handleNewGame()` resetting `gameState = initGame()` (score=0) does NOT reset bestScore
+- When a new game starts, `gameState.score` becomes 0, which is NOT > bestScore, so bestScore stays
+
+### ScoreBoard Component
+
+`ScoreBoard.svelte` already accepts `score` and `bestScore` props — no changes needed to the component:
+
+```svelte
+let { score = 0, bestScore = 0 } = $props();
+```
+
+The only change is in `App.svelte` line 58: replace `bestScore={0}` with `bestScore={bestScore}`.
+
+### Previous Story Intelligence
+
+From Epic 1 implementation:
+- `App.svelte` owns all state via `$state` rune — `gameState` is the single game state object
+- `ScoreBoard` component at `src/components/ScoreBoard.svelte` — presentational, receives `score` and `bestScore` props
+- `handleNewGame()` calls `gameState = initGame()` which returns `{ grid, score: 0, won: false, keepPlaying: false }`
+- `getDirectionFromKey` is the export name from `input-handler.js` (not `mapKeyToDirection`)
+- `overlayType` is used instead of separate `gameOver`/`won` checks in the template
+- Existing test suite: 38 tests in `src/lib/game-logic.test.js` — all game logic, no UI tests
+
+### Scope Boundary
+
+This story is intentionally minimal:
+- **In scope:** In-memory best score tracking that survives New Game within a session
+- **Out of scope:** localStorage persistence (Story 2.2), game state persistence (Story 2.2), keep-playing mode changes (Story 2.3)
+
+### References
+
+- [Source: _bmad-output/planning-artifacts/epics.md#Story 2.1]
+- [Source: _bmad-output/planning-artifacts/architecture.md#Frontend Architecture - State Management]
+- [Source: _bmad-output/planning-artifacts/architecture.md#Implementation Patterns - Communication Patterns]
+
+## Dev Agent Record
+
+### Agent Model Used
+
+### Debug Log References
+
+### Completion Notes List
+
+### File List

bmad/_bmad-output/implementation-artifacts/deferred-work.md

@@ -0,0 +1,10 @@
+# Deferred Work
+
+## Deferred from: code review of Epic 1 (2026-04-13)
+
+- **Best score always 0, never tracked** — UI displays "BEST: 0" that never updates. Covered by Story 2-1 (Best Score Tracking).
+- **Tile keyed by position, not identity** — `Grid.svelte` keys tiles by `r-c` grid position instead of unique tile ID. Will break slide/merge animations. Address in Epic 3 (animations).
+- **No animation lock for rapid key input** — No debounce or move-in-progress guard in `handleKeydown`. Synchronous now but will need a lock when animations are added in Epic 3.
+- **Grid 500px overflow on narrow viewports** — `Grid.svelte` hardcodes `containerSize = 500`. Overflows on mobile. Covered by Story 4-3 (Responsive Layout).
+- **Tile font overflow for very large values** — 3-tier font sizing (55/45/35px) exists but values beyond 8192 (6+ digits) may overflow the 106px cell at 35px. Epic 5 polish.
+- **Overlay has no keyboard focus trap** — `GameMessage.svelte` does not trap focus or auto-focus the action button. Accessibility improvement for post-MVP.

bmad/_bmad-output/implementation-artifacts/sprint-status.yaml

@@ -35,7 +35,7 @@
 # - Dev moves story to 'review', then runs code-review (fresh context, different LLM recommended)
 
 generated: 2026-04-13
-last_updated: 2026-04-13T01:00:00
+last_updated: 2026-04-13T22:21:00
 project: try-bmad
 project_key: NOKEY
 tracking_system: file-system
@@ -43,18 +43,18 @@ story_location: _bmad-output/implementation-artifacts
 
 development_status:
   # Epic 1: Play a Complete Game (Desktop)
-  epic-1: in-progress
-  1-1-project-scaffold-and-dev-environment: review
-  1-2-game-logic-module: review
-  1-3-game-board-and-tile-rendering: review
-  1-4-game-header-score-display-and-new-game-button: review
-  1-5-keyboard-input-and-interactive-gameplay: review
-  1-6-win-and-game-over-overlays: review
+  epic-1: done
+  1-1-project-scaffold-and-dev-environment: done
+  1-2-game-logic-module: done
+  1-3-game-board-and-tile-rendering: done
+  1-4-game-header-score-display-and-new-game-button: done
+  1-5-keyboard-input-and-interactive-gameplay: done
+  1-6-win-and-game-over-overlays: done
   epic-1-retrospective: optional
 
   # Epic 2: Save Progress & Keep Playing
-  epic-2: backlog
-  2-1-best-score-tracking: backlog
+  epic-2: in-progress
+  2-1-best-score-tracking: ready-for-dev
   2-2-game-state-persistence: backlog
   2-3-keep-playing-mode: backlog
   epic-2-retrospective: optional