# Implementation Plan: Inline HP Delta Input

**Branch**: `014-inline-hp-delta` | **Date**: 2026-03-05 | **Spec**: [spec.md](./spec.md)
**Input**: Feature specification from `/specs/014-inline-hp-delta/spec.md`

## Summary

Replace the existing QuickHpInput component (which uses a damage/heal mode toggle) with a simpler inline HP delta input. Users type a number and press Enter to apply damage by default, or click explicit damage/heal buttons. No domain changes needed -- the existing `adjustHp` pure function already accepts positive and negative deltas. This is a UI-only refactor of the quick HP input component.

## Technical Context

**Language/Version**: TypeScript 5.8 (strict mode, verbatimModuleSyntax)
**Primary Dependencies**: React 19, Vite 6, Tailwind CSS v4, shadcn/ui-style components, Lucide React (icons)
**Storage**: N/A (no storage changes -- existing localStorage persistence unchanged)
**Testing**: Vitest
**Target Platform**: Web browser (local-first, single-user)
**Project Type**: Web application (monorepo: domain + application + web adapter)
**Performance Goals**: Instant feedback on HP adjustment (<100ms perceived)
**Constraints**: Local-first, single-user MVP
**Scale/Scope**: Single encounter screen, ~1-20 combatants

## Constitution Check

*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*

| Principle | Status | Notes |
|-----------|--------|-------|
| I. Deterministic Domain Core | PASS | No domain changes. Existing `adjustHp` is a pure function. |
| II. Layered Architecture | PASS | Change is entirely in the adapter layer (web UI). Domain and application layers unchanged. |
| III. Agent Boundary | N/A | No agent features involved. |
| IV. Clarification-First | PASS | Spec is clear; no ambiguities remain. |
| V. Escalation Gates | PASS | Feature is within spec scope -- replacing existing UI with simplified version. |
| VI. MVP Baseline Language | PASS | Assumptions use "MVP baseline does not include" language. |
| VII. No Gameplay Rules | PASS | No gameplay mechanics in this feature. |

**Gate result**: PASS -- all principles satisfied.

## Project Structure

### Documentation (this feature)

```text
specs/014-inline-hp-delta/
├── plan.md              # This file
├── research.md          # Phase 0 output
├── data-model.md        # Phase 1 output
├── quickstart.md        # Phase 1 output
└── tasks.md             # Phase 2 output (/speckit.tasks command)
```

### Source Code (repository root)

```text
packages/domain/src/
├── adjust-hp.ts              # Existing — no changes needed
├── types.ts                  # Existing — no changes needed
└── __tests__/adjust-hp.test.ts  # Existing — no changes needed

packages/application/src/
└── adjust-hp-use-case.ts     # Existing — no changes needed

apps/web/src/
├── components/
│   ├── quick-hp-input.tsx    # MODIFY — replace mode toggle with damage/heal buttons
│   └── combatant-row.tsx     # Existing — integration point (no changes expected)
└── hooks/
    └── use-encounter.ts      # Existing — no changes needed
```

**Structure Decision**: Existing monorepo structure (domain → application → web adapter) is used. This feature only modifies the web adapter layer, specifically the `quick-hp-input.tsx` component. No new files or packages needed.