gijs_pong/.planning/STATE.md

---
gsd_state_version: 1.0
milestone: v1.0
milestone_name: milestone
status: unknown
stopped_at: Completed 02-01-PLAN.md
last_updated: "2026-03-10T20:07:22.163Z"
progress:
  total_phases: 5
  completed_phases: 1
  total_plans: 4
  completed_plans: 3
---

# STATE: Super Pong Next Gen

**Project Reference**
- **Core Value:** Pong reimagined with juice and depth — spectacular visuals, rich mechanics, complete game experience
- **Current Focus:** Phase 1 — executing plans
- **Key Constraint:** Coarse granularity (5 phases max), HTML5 Canvas + vanilla JS, static deployment

---

## Current Position

| Attribute | Value |
|-----------|-------|
| **Phase** | 02-core-gameplay |
| **Plan** | Plan 1/2 — COMPLETE |
| **Status** | Phase 02 in progress — paddle2, AI module, predictive ray-cast, 3 difficulty levels done |
| **Progress** | 75% (3/4 plans complete; Phase 1 complete, Phase 2 plan 1 complete) |

```
[████████░░] 75% — Phase 2: 1/2 plans complete
```

---

## Performance Metrics

| Metric | Target | Status |
|--------|--------|--------|
| **Phase Coverage** | 100% (37/37 requirements mapped) | ✓ Complete |
| **Success Criteria** | 2-5 per phase | ✓ Complete |
| **Dependency Chain** | Linear (P1 → P2 → P3 → P4 → P5) | ✓ Validated |
| **01-01 Duration** | — | 1 min (2 tasks, 1 file) |

| **01-02 Duration** | — | 1 min (2 tasks, 1 file) |

---
| Phase 02-core-gameplay P01 | 2min | 2 tasks | 1 files |

## Accumulated Context

### Key Decisions Made

1. **Coarse Granularity Compression:** Research suggested 10 phases; compressed to 5 by merging:
   - Game loop + input + physics = Phase 1
   - Second paddle + AI = Phase 2
   - Menus + audio + pause = Phase 3
   - Visual effects + power-ups + arenas = Phase 4
   - Performance + testing = Phase 5

2. **Phase 5 (Release) Has No Requirements:** All 37 v1 requirements covered by phases 1-4. Phase 5 is purely validation (cross-browser, performance, pitfall mitigation).

3. **Success Criteria Grounded in Research Pitfalls:** Each phase's criteria address critical pitfalls from research:
   - Phase 1: DPI scaling, game loop timing
   - Phase 2: Ball tunneling, input lag, AI balance
   - Phase 3: Audio autoplay policy
   - Phase 4: Power-up balance
   - Phase 5: Performance, memory leaks, cross-browser

4. **deltaTime Cap at 50ms:** Game loop caps deltaTime to prevent physics explosion when tab loses focus and resumes — without this a single large delta would fling the ball off screen.

5. **Logical vs Bitmap Coordinate Separation:** canvas.width/height = logical * devicePixelRatio; ctx.scale(dpr, dpr) makes all game draw calls use logical pixels — correct HiDPI approach for sharp rendering on Retina displays.

6. **Module-Object Pattern Established:** GameLoop, Renderer, Input, Physics, GameState are plain JS objects with init() methods in a single script tag. No classes, no modules, no build step — runs directly from filesystem.

7. **e.code over e.key for Input:** Using e.code === 'KeyW' makes W/S detection layout-independent (works on AZERTY and other non-QWERTY keyboards).

8. **Zone angles [-60, -30, 5, 30, 60] degrees:** Center zone uses 5 deg not 0 to prevent infinite horizontal ball loops; top/bottom edges at 60 degrees for dramatic deflection.

9. **GameConfig centralizes tunable constants:** initialBallSpeed (220px/s), speedIncrement (18px/s), paddleSpeed (400px/s) — all adjustable without touching Physics logic.

10. **vx/vy recomputed from speed+angle each paddle hit:** Prevents compound rounding drift from repeated scaling; speed and direction always cleanly separated.

11. **AI uses predictive ray-cast with wall bounce simulation:** _predictBallY steps forward in time (up to 500 steps) simulating wall bounces — far more accurate than linear Y interpolation.

12. **AI difficulty presets as config objects:** { speed, reactionDelay, errorMargin } in GameConfig — all three dimensions of difficulty tunable without touching AI logic.

13. **AI waits when ball moves toward player (vx < 0):** Resets reaction timer and returns early — AI only acts when ball is heading toward its paddle, avoiding premature repositioning.

14. **Physics.onResize() calls init() for full reposition:** Ensures paddle2 (and paddle1) are properly repositioned on window resize rather than just updating width/height dimensions.

### Coverage Validation

**Total v1 Requirements:** 37
- CORE (8): All mapped to Phase 1-2
- AI (4): All mapped to Phase 2
- SCRN (4): All mapped to Phase 3
- VFX (5): All mapped to Phase 1 (DPI) and Phase 4 (particles/glow/trails/shake)
- PWR (7): All mapped to Phase 4
- ARENA (4): All mapped to Phase 4
- AUD (5): All mapped to Phase 3

**Unmapped Requirements:** 0 ✓
**Coverage:** 100% ✓

### Research Alignment

- Phase 1 addresses Research Pitfalls: #1 (Game Loop Timing), #2 (Canvas DPI Scaling)
- Phase 2 addresses Research Pitfalls: #3 (Ball Tunneling), #4 (Input Lag), #5 (AI Difficulty Balance)
- Phase 3 addresses Research Pitfall: #6 (WebAudio Autoplay Policy)
- Phase 4 addresses Research Pitfalls: #7 (Power-Up Balance)
- Phase 5 addresses Research Pitfall: #8 (Memory Leaks)

---

## Session Continuity

### What Just Happened

Phase 02 Plan 01 executed: paddle2 added to GameState (mirrors paddle1 structure), Input extended with ArrowUp/ArrowDown + named handler refs + cleanup(), AI module added with predictive ray-cast interception (wall-bounce simulation) and 3 difficulty presets (AI_EASY/MEDIUM/HARD). Physics._checkPaddle2Collision() added with 5-zone deflection sending ball LEFT. Physics.update() extended with paddle2 movement branch. Requirements CORE-08, AI-01, AI-02, AI-03, AI-04 satisfied.

### What Comes Next

1. Execute Phase 2 Plan 02 — mode selection UI, scoring system, win/game-over states, ball tunneling safeguards
2. Continue through phases 3-5 after Phase 2 complete

### Known Blockers

None.

### Decisions Pending

None.

### Last Session

Stopped at: Completed 02-01-PLAN.md

---

*State initialized: 2026-03-10*