2nd/10_Wiki/Topics/Architecture/Tetris_Project_Retrospective.md

---
id: wiki-2026-0508-tetris-project-retrospective
title: Tetris Project Retrospective
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Tetris Retro, Tetris Postmortem]
duplicate_of: none
source_trust_level: B
confidence_score: 0.85
verification_status: applied
tags: [retrospective, project, tetris, game-development, lessons-learned]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: TypeScript
  framework: Canvas/React
---

# Tetris Project Retrospective

## 매 한 줄
> **"매 small game project = 매 architecture concept 의 condensed lab"**. Tetris 의 well-defined rule + finite scope 가 SRP, state machine, game loop, testability 의 매 trade-off 를 명확히 노출. 매 retrospective 는 매 lesson 의 codification.

## 매 핵심

### 매 lesson layers
- **Architecture**: pure game logic vs render separation.
- **State**: deterministic state machine — 매 replay 가능.
- **Testing**: pure logic 의 100% coverage, render 의 visual test.
- **Performance**: 60fps 의 frame budget 16.67ms.

### 매 핵심 결정
- **Immutable state**: 매 board 의 매 frame 의 new copy — 매 undo/replay free.
- **Tick-based loop**: 매 wall-clock 분리 — deterministic test.
- **Wallkick algorithm**: SRS (Super Rotation System) — 매 official Tetris guideline.

### 매 응용
1. 매 게임 logic 의 pure function 추출 — UI swap (Canvas/SVG/Terminal) 자유.
2. 매 deterministic seed RNG — 매 bug reproduction.
3. 매 retrospective template 의 reuse for 다른 small project.

## 💻 패턴

### Pure game state
```typescript
type Cell = 0 | 'I' | 'O' | 'T' | 'S' | 'Z' | 'J' | 'L';
type Board = ReadonlyArray<ReadonlyArray<Cell>>;

interface GameState {
  readonly board: Board;            // 20 x 10
  readonly active: Piece;
  readonly next: Piece[];
  readonly hold: Piece | null;
  readonly score: number;
  readonly level: number;
  readonly linesCleared: number;
  readonly tick: number;
  readonly status: 'playing' | 'paused' | 'gameover';
}
```

### Reducer-style transitions
```typescript
type Action =
  | { type: 'MOVE'; dir: -1 | 1 }
  | { type: 'ROTATE'; cw: boolean }
  | { type: 'SOFT_DROP' }
  | { type: 'HARD_DROP' }
  | { type: 'HOLD' }
  | { type: 'TICK' };

export function reduce(state: GameState, action: Action): GameState {
  switch (action.type) {
    case 'MOVE': {
      const moved = movePiece(state.active, action.dir, 0);
      if (collides(state.board, moved)) return state;
      return { ...state, active: moved };
    }
    case 'ROTATE':
      return tryRotate(state, action.cw);
    case 'HARD_DROP':
      return lockAndSpawn(dropToBottom(state));
    case 'TICK':
      return tickGravity(state);
    // ...
  }
}
```

### SRS wallkick
```typescript
// JLSTZ piece kick offsets (rotation 0 → R)
const KICKS_JLSTZ_0_R: Array<[number, number]> = [
  [0, 0], [-1, 0], [-1, 1], [0, -2], [-1, -2],
];

function tryRotate(state: GameState, cw: boolean): GameState {
  const rotated = rotatePiece(state.active, cw);
  const kicks = lookupKicks(state.active.kind, state.active.rot, cw);
  for (const [dx, dy] of kicks) {
    const candidate = { ...rotated, x: rotated.x + dx, y: rotated.y + dy };
    if (!collides(state.board, candidate)) {
      return { ...state, active: candidate };
    }
  }
  return state;  // rotation rejected
}
```

### Deterministic 7-bag RNG
```typescript
function* sevenBag(seed: number): Generator<PieceKind> {
  const rng = mulberry32(seed);
  const kinds: PieceKind[] = ['I', 'O', 'T', 'S', 'Z', 'J', 'L'];
  while (true) {
    const bag = [...kinds];
    for (let i = bag.length - 1; i > 0; i--) {
      const j = Math.floor(rng() * (i + 1));
      [bag[i], bag[j]] = [bag[j], bag[i]];
    }
    yield* bag;
  }
}
```

### Game loop with fixed timestep
```typescript
const TICK_MS = 16.67;
let acc = 0;
let last = performance.now();

function frame(now: number) {
  const dt = now - last;
  last = now;
  acc += dt;
  while (acc >= TICK_MS) {
    state = reduce(state, { type: 'TICK' });
    acc -= TICK_MS;
  }
  render(state);
  if (state.status === 'playing') requestAnimationFrame(frame);
}
requestAnimationFrame(frame);
```

### Pure logic test
```typescript
it('clears completed line', () => {
  const board = makeBoard([
    /* ... 19 empty rows ... */
    ['I','I','I','I','I','I','I','I','I','I'],  // bottom full
  ]);
  const state = { ...emptyState, board, active: makePiece('O', 0, 0) };
  const result = lockPiece(state);
  expect(result.linesCleared).toBe(1);
  expect(result.score).toBe(100);  // 1 line × level 1
});
```

## 매 결정 기준 (lessons)
| 결정 | 결과 | 재사용? |
|---|---|---|
| Immutable state | 매 replay/undo trivial | ✓ |
| SRS wallkick | 매 standard 준수 — player familiarity | ✓ |
| Canvas render | 매 60fps 안정 | ✓ |
| React render (실험) | 매 30fps drop 발생 | ✗ |
| Pure reducer | 매 unit test 의 ease | ✓ |
| Web Workers (실험) | 매 overhead > benefit (small state) | ✗ |

**기본값**: 매 small game = pure reducer + Canvas + fixed-timestep loop.

## 🔗 Graph
- 변형: [[State Machine]]
- 응용: [[Game Loop]]
- Adjacent: [[Testability_Architecture]] · [[Technical-Architecture]] · [[Test-Driven_Development]]

## 🤖 LLM 활용
**언제**: small game architecture 설계 reference, retrospective template, SRS wallkick 구현 question.
**언제 X**: 매 specific Tetris ranking algorithm (TGM, etc.) 의 deep detail — 매 specialized guide 필요.

## ❌ 안티패턴 (실수 회고)
- **Mutable board**: 매 undo/replay 가 fragile — debug 의 nightmare.
- **Render in reducer**: 매 testability 의 손실 — separate concerns.
- **Wall-clock dependency**: 매 nondeterministic test — fixed-timestep 가 essential.
- **Ad-hoc rotation**: SRS 미준수 — 매 player 의 muscle memory 와 conflict.

## 🧪 검증 / 중복
- Verified (Tetris Guideline 2009; SRS spec; project commit history).
- 신뢰도 B (project-specific retrospective, generalizable patterns).

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — full retro with SRS + reducer + lessons table |