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# Implementation Summary

**Session ID**: `phase02-session04-battlefield-state-and-interaction-polish` **Package**: `apps/web` **Completed**: 2026-05-29 **Duration**: 3 hours

***

## Overview

This session completed the app-side 2D battlefield interaction polish for `apps/web`. The work hardened hero token accessibility and selection semantics, preserved synchronization with the existing roster and detail state, improved empty-board clearing, and kept battlefield state readable across active, awaiting input, verifying, error, spawning, dismissed, selected, and idle conditions.

It also tightened fallback rendering for missing assets, kept reduced-motion behavior meaningful, bounded achievement bursts, and added focused component, helper, and celebration tests to cover the updated battlefield contract.

***

## Deliverables

### Files Created

| File                                                                                                      | Purpose                                          | Lines |
| --------------------------------------------------------------------------------------------------------- | ------------------------------------------------ | ----- |
| `.spec_system/specs/phase02-session04-battlefield-state-and-interaction-polish/implementation-notes.md`   | Session log, task trace, and validation evidence | \~360 |
| `.spec_system/specs/phase02-session04-battlefield-state-and-interaction-polish/IMPLEMENTATION_SUMMARY.md` | Final session summary and closeout record        | \~80  |
| `apps/web/tests/BattlefieldInteraction.test.tsx`                                                          | Focused battlefield interaction coverage         | \~220 |

### Files Modified

| File                                                                               | Changes                                                                                                      |
| ---------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------ |
| `apps/web/src/components/battlefield/Battlefield.tsx`                              | Hardened token accessible names, selection semantics, state labels, fallback surfaces, and cleanup behavior. |
| `apps/web/src/lib/battlefield2d.ts`                                                | Refined coordinate normalization and label placement behavior.                                               |
| `apps/web/src/components/battlefield/achievementCelebration.ts`                    | Kept burst diffing, capping, tone generation, and timer cleanup testable.                                    |
| `apps/web/src/index.css`                                                           | Refined battlefield, token, selected, fallback, and reduced-motion styling.                                  |
| `apps/web/tests/Battlefield.test.tsx`                                              | Extended coverage for battlefield selection and visible state treatment.                                     |
| `apps/web/tests/battlefield2d.test.ts`                                             | Extended helper coverage for clamping and edge-case placement.                                               |
| `apps/web/tests/achievementCelebration.test.ts`                                    | Extended celebration coverage for diffing, caps, cleanup, and reduced motion.                                |
| `docs/battlefield.md`                                                              | Documented the updated battlefield interaction and fallback contract.                                        |
| `apps/web/README_web.md`                                                           | Recorded the app-side battlefield contract and deferred parity boundary.                                     |
| `.spec_system/state.json`                                                          | Marked the session complete and cleared the active session pointer.                                          |
| `.spec_system/PRD/phase_02/PRD_phase_02.md`                                        | Marked session 04 complete and advanced phase progress.                                                      |
| `.spec_system/PRD/phase_02/session_04_battlefield_state_and_interaction_polish.md` | Marked the session tracker complete and recorded validation.                                                 |
| `.spec_system/PRD/PRD.md`                                                          | Marked Phase 02 as in progress in the master PRD.                                                            |
| `apps/web/package.json`                                                            | Bumped the web package patch version.                                                                        |

***

## Technical Decisions

1. **Native controls for hero tokens**: Keeping battlefield heroes as buttons preserves keyboard activation, assistive semantics, and explicit selected state.
2. **Pure helper boundaries**: Coordinate clamping and label placement stay in the helper layer so the behavior remains easy to test without rendering the full app.
3. **Bounded async cleanup**: Achievement bursts stay capped and timer-cleaned so the battlefield remains stable under repeated updates and unmounts.

***

## Test Results

| Metric              | Value     |
| ------------------- | --------- |
| Focused tests       | 97 passed |
| Typecheck           | Passed    |
| Lint                | Passed    |
| ASCII and LF checks | Passed    |

***

## Lessons Learned

1. Battlefield readability needs text and structural cues, not color alone, to stay usable in reduced-motion and failure states.
2. Session closeout needs both state tracking and phase tracker updates so the spec workflow does not drift from the implementation record.

***

## Future Considerations

Items for future sessions:

1. Complete Phase 02 Session 05 for battlefield asset and public demo parity.
2. Keep Session 06 focused on settings, replay, notification, and scan UX boundaries.

***

## Session Statistics

* **Tasks**: 21 completed
* **Files Created**: 3
* **Files Modified**: 14
* **Tests Added**: 4
* **Blockers**: 0 resolved


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