# Data Model: HP Status Indicators

**Feature**: 013-hp-status-indicators
**Date**: 2026-03-05

## Entities

### HpStatus (derived type -- not stored)

A discriminated string union representing the health state of a combatant.

| Value | Condition | Description |
|-------|-----------|-------------|
| `"healthy"` | `currentHp >= maxHp / 2` | Combatant is above half HP |
| `"bloodied"` | `0 < currentHp < maxHp / 2` | Combatant is below half HP but still conscious |
| `"unconscious"` | `currentHp <= 0` | Combatant is at or below zero HP |

**Derivation rules**:
- Only meaningful when both `currentHp` and `maxHp` are defined
- Returns `undefined` when either value is missing (HP tracking not enabled)
- Evaluation order: check `unconscious` first (currentHp <= 0), then `bloodied` (currentHp < maxHp / 2), else `healthy`

### Combatant (existing -- unchanged)

No modifications to the `Combatant` interface. HP status is computed on demand from existing fields:

| Field | Type | Used for status |
|-------|------|----------------|
| `currentHp` | `number \| undefined` | Compared against thresholds |
| `maxHp` | `number \| undefined` | Defines the "half HP" bloodied threshold |

## State Transitions

HP status changes are a side effect of existing HP operations (adjustHp, setHp). No new state transitions are introduced.

```text
healthy ──[take damage below half]──> bloodied
bloodied ──[take damage to 0]──────> unconscious
unconscious ──[heal above 0]───────> bloodied or healthy
bloodied ──[heal above half]───────> healthy
healthy ──[take massive damage]────> unconscious (skip bloodied)
```

## Storage Impact

None. HP status is derived at render time from existing persisted `currentHp` and `maxHp` values. No localStorage schema changes.