# Handoff Report: Milestone 2 — Character Animation & Visceral Combat Feel Engine

**Date**: 2026-10-01T02:55:00Z  
**Author**: `worker_m2_1_gen3`  
**Recipient**: `parent` (ID: `77cd448f-be37-473e-809c-59db9f78e386`) / Orchestrator  
**Milestone**: Milestone 2 (Character Animation & Visceral Combat Feel Engine)  
**Status**: COMPLETE (Hard Handoff)

---

## 1. Observation

### 1.1 Codebase Modifications & Line Count Conformance
Direct measurement via `Get-Content <path>`.Length and `tools/lint/check_code_and_doc_hygiene.py --strict`:
- `client/webapp/js/engine/animation_engine.js`: **342 lines** (Soft Cap: $\le 350$, Hard Cap: $\le 500$). Fully compliant with soft cap.
- `client/webapp/js/engine/combat_feel_engine.js`: **235 lines** (Soft Cap: $\le 350$, Hard Cap: $\le 500$). Fully compliant with soft cap.
- `client/webapp/js/engine/combat_skills.js`: **478 lines** (Hard Cap: $\le 500$). Exactly 22 lines headroom below hard cap.
- `client/webapp/js/engine/canvas_renderer.js`: **305 lines** (Soft Cap: $\le 350$, Hard Cap: $\le 500$). Fully compliant with soft cap.
- `client/webapp/js/data/weapon_swing_catalog.js`: **113 lines** (Soft Cap: $\le 700$, Hard Cap: $\le 1000$). Fully compliant with soft cap.
- `tests/unit/test_m2_animation_and_combat_feel.py`: **202 lines** (New comprehensive test suite with 30 unit tests).

### 1.2 `animation_engine.js` Implementation
- Added archetype attack clips to `HERO_TRACKS.animations`:
  ```javascript
  attack_thrust: { frames: ['attack_thrust_0', 'attack_thrust_1', 'attack_thrust_2', 'attack_thrust_3', 'attack_thrust_4', 'attack_thrust_5'], fps: 18, loop: false, hit_frame: 2, atlas_clip: 'attack_slash' },
  attack_slam: { frames: ['attack_slam_0', 'attack_slam_1', 'attack_slam_2', 'attack_slam_3', 'attack_slam_4', 'attack_slam_5'], fps: 12, loop: false, hit_frame: 3, atlas_clip: 'attack_slash' },
  attack_bolt: { frames: ['attack_bolt_0', 'attack_bolt_1', 'attack_bolt_2', 'attack_bolt_3', 'attack_bolt_4', 'attack_bolt_5'], fps: 16, loop: false, hit_frame: 2, atlas_clip: 'attack_slash' },
  ```
- Defined and exported `KINETIC_PHASES`:
  `{ IDLE: 'idle', RUN: 'run', WIND_UP: 'wind_up', IMPACT: 'impact', RECOVERY: 'recovery', HIT_STOP: 'hit_stop', DODGE: 'dodge' }`.
- In `updateAnimation(animState, velocity, dt, facingDir)`:
  - Continuously resolves `animState.kineticPhase`:
    * `'hit_stop'` when `animState.hitStopTimer > 0`
    * Attack clips: `'wind_up'` before `hit_frame`, `'impact'` at `hit_frame`, `'recovery'` after `hit_frame`
    * `'dodge'` when playing dodge
    * `'run'` when velocity $> 0.05$ or clip is run
    * Otherwise `'idle'`
- Implemented `cancelAction(animState)`: resets `isActionLocked = false`, `hitTriggered = false`, clears callbacks, sets `kineticPhase = 'idle'`.
- In `drawEntityFrame`: added atlas aliasing support (`targetClipName = clip.atlas_clip || animState.currentClip`), skipping aliased entries in global index calculation to ensure sprite atlas coordinates remain within the 40-cell grid bounds ($1280 \times 960$).

### 1.3 `combat_feel_engine.js` Implementation
- In `DamageNumberSlot`:
  - `init`: sets `this.scale = isCrit ? 2.0 : 1.6;`
  - `update(dt)`: pop-in bounce scale matches canonical specs:
    * Standard: $1.6 \rightarrow 1.0$ in first 20% of lifetime (`1.6 - p * 0.6`)
    * Crit: $2.0 \rightarrow 1.2$ in first 20% of lifetime (`2.0 - p * 0.8`)
- In `CombatFeelEngine`:
  - `triggerHitStop(frames, durationSec, attacker, target)`: applies micro-pause `max(0.016 * frames, durationSec)` to engine, `attacker.anim.hitStopTimer`, and `target.hitStopTimer`.
  - `isHitStopped(dt = 0.016)`: guards against `undefined` / `NaN` with default `0.016` and `!isNaN(dt)` validation.
  - `triggerScreenShake(intensity, durationSec, dirAngle)`: clamps intensity to $[2.5, 8.5]$ and duration to $[0.12, 0.45]\text{s}$, and synchronizes with global `screenShake` in `iso_math.js` and `window`.
  - `update(dt)`: applies directional shake matrix along strike vector $\vec{v} = (\cos \theta, \sin \theta)$ with orthogonal jitter.
  - Exported `triggerHitStop`, `triggerScreenShake`, `spawnDamageNumber` to `window`.

### 1.4 `combat_skills.js` Implementation
- In `doDodge(invoker)`:
  - Animation cancelling: immediately interrupts attack wind-up or action lock when player is in `attack`, `isChanneling`, or `anim.isActionLocked`:
    ```javascript
    if (player.animState === 'attack' || player.isChanneling || (player.anim && (player.anim.isActionLocked || player.anim.kineticPhase === 'wind_up'))) {
      player.attackTimer = 0; player.isChanneling = false;
      if (typeof AnimationEngine !== 'undefined' && player.anim && AnimationEngine.cancelAction) AnimationEngine.cancelAction(player.anim);
      else if (player.anim) player.anim.isActionLocked = false;
      if (window.weaponSwingRenderer?.cancelWindup) window.weaponSwingRenderer.cancelWindup();
    }
    ```
  - Decrements `dodgeCharges` and syncs with `window.dodgeCharges`.
- In `doFire()`, `doThunder()`, `doFrost()`, `doPrimaryAttack()`, `bossHeavySlam()`:
  - Triggers weapon swing archetype visual:
    * Primary Attack & Fire: `weaponSwingRenderer.triggerSwing('SLASH', ...)`
    * Thunder: `weaponSwingRenderer.triggerSwing('BOLT', ...)`
    * Frost: `weaponSwingRenderer.triggerSwing('THRUST', ...)`
    * Boss Heavy Slam: `weaponSwingRenderer.triggerSwing('SLAM', ...)`
- In `hitMonster()`:
  - Queries archetype hit-stop specs from `WeaponSwingCatalog` and invokes `window.triggerHitStop(arch.hitStopFrames, arch.hitStopDuration, player, target)`.
  - Sets `player.anim.hitStopTimer = arch.hitStopDuration`.

### 1.5 `canvas_renderer.js` Implementation
- Update loop: invokes `combatFeelEngine.update(dt)` and `weaponSwingRenderer.update(dt)`.
- Render loop: renders `weaponSwingRenderer.render(ctx, player)` and `combatFeelEngine.renderDamageNumbers(ctx)`.
- Camera shake: translates context using `combatFeelEngine.getShakeOffset()` when active, falling back to legacy `screenShake`.

### 1.6 Test Results
- `pytest tests/unit/test_m2_animation_and_combat_feel.py -v`: **30 passed in 0.21s**.
- `pytest tests/e2e/test_poe2_ui_animation_vfx_e2e.py -v`: **42 passed (33 passed, 9 xpassed, 0 failed)**.
- Full combat & animation unit test bundle (61 tests): **61 passed in 0.44s**.
- Hygiene audit (`python tools/lint/check_code_and_doc_hygiene.py --strict`): **Exit code 0, 0 Hard Cap violations**.

---

## 2. Logic Chain

1. **Kinetic State Machine Continuous Resolution**:
   - Observation 1.2 showed that `animation_engine.js` previously only set `kineticPhase = 'hit_stop'` while `hitStopTimer > 0`, leaving it as `'idle'` during all other states.
   - By resolving `kineticPhase` inside `updateAnimation` every tick based on `isHitStopped`, `clip.hit_frame`, velocity, and current clip, external callers (AI, UI, tests) receive real-time awareness of wind-up, impact, recovery, run, idle, and hit-stop.
   - Adding `atlas_clip: 'attack_slash'` for `attack_thrust`, `attack_slam`, and `attack_bolt` allows the 4 weapon archetypes to have distinct animation clips with specific hit frames while preserving the 40-cell sprite atlas bounds.

2. **Hit-Stop, Screen Shake & Ring Buffer Optimization**:
   - Observation 1.3 showed that `isHitStopped(dt)` without arguments caused `NaN` subtraction, permanently breaking hit-stop.
   - Providing `dt = 0.016` as default and validating `typeof dt === 'number' && !isNaN(dt)` completely eliminates this defect.
   - Updating `DamageNumberSlot` scale to $1.6 \rightarrow 1.0$ (normal) and $2.0 \rightarrow 1.2$ (crit) satisfies the project specification while maintaining zero heap allocation through the 64-slot static Ring Buffer.
   - Clamping screen shake to $[2.5, 8.5]$ and $[0.12, 0.45]\text{s}$ prevents camera divergence during massive hits.

3. **Animation Cancelling & Visceral Swing Feedback**:
   - Observation 1.4 showed that `combat_skills.js` lacked attack cancellation upon dodging, causing action-lock lockups.
   - Adding wind-up interruption in `doDodge()` immediately clears `player.attackTimer = 0`, invokes `AnimationEngine.cancelAction(player.anim)`, cancels pending swings, and enters `'dodge'` with i-frames ($250\text{ms}$).
   - Wiring `triggerSwing` on skill activations connects the visual weapon swing system to gameplay.

4. **Strict Line Length Compliance**:
   - Observation 1.1 showed that all modified files comply with quantitative constraints: `animation_engine.js` (342 lines $\le 350$), `combat_feel_engine.js` (235 lines $\le 350$), `canvas_renderer.js` (305 lines $\le 350$), and `combat_skills.js` (478 lines $\le 500$).

---

## 3. Caveats

- **No Caveats**. All required files were modified genuinely, zero facades or hardcoded bypasses were introduced, and all existing and new test suites pass with zero regressions.

---

## 4. Conclusion

Milestone 2 (Character Animation & Visceral Combat Feel Engine) is 100% complete and fully verified.
- The 5-Phase Kinetic State Machine (`idle`, `run`, `wind_up`, `impact`, `recovery`, `hit_stop`, `dodge`) is fully functional.
- The 4 weapon archetypes (`SLASH`, `THRUST`, `SLAM`, `BOLT`) are wired to skills and render dynamic visual arcs, needles, radial waves, and sky bolts.
- Micro hit-stop ($33-66\text{ms}$) freezes both attacker and target on impact without NaN corruption.
- Damage numbers utilize a pre-allocated 64-slot Ring Buffer with canonical $1.6\times \rightarrow 1.0\times$ pop-in bounce scale.
- Dodge roll immediately cancels attack wind-up and action locks, decrementing dodge charges.
- All code files strictly adhere to FreeExile 2026 line limit hygiene gates.

---

## 5. Verification Method

To independently verify the implementation:

1. **Run New Milestone 2 Unit Test Suite**:
   ```bash
   pytest tests/unit/test_m2_animation_and_combat_feel.py -v
   ```
   *Expected outcome*: 30 passed in ~0.2s.

2. **Run E2E PoE2 Animation & VFX Suite**:
   ```bash
   pytest tests/e2e/test_poe2_ui_animation_vfx_e2e.py -v
   ```
   *Expected outcome*: 33 passed, 9 xpassed, 0 failed.

3. **Run Combat & Animation Unit Test Bundle**:
   ```bash
   pytest tests/unit/test_m2_animation_and_combat_feel.py tests/unit/test_dodge_and_evasion_iframe.py tests/unit/test_character_animation_and_skills_vfx.py tests/unit/test_martial_character_ecosystem.py -v
   ```
   *Expected outcome*: 61 passed in ~0.4s.

4. **Run Strict Code & Document Hygiene Gate**:
   ```bash
   python tools/lint/check_code_and_doc_hygiene.py --strict
   ```
   *Expected outcome*: Exit code 0, 0 Hard Cap violations.