docs/crossword-app-plan.md

# Crossword Puzzle Webapp - Complete Implementation Plan

## Architecture Overview

**Frontend (React/Vue/Vanilla JS)**
- Topic selection dropdown/buttons
- Generate puzzle button
- Interactive crossword grid display
- Clue lists (across/down)

**Backend (Node.js/Python/Go)**
- REST API endpoints for puzzle generation
- Crossword algorithm implementation
- Word/clue database management

**Database**
- Word collections organized by topics
- Clue-answer pairs
- Pre-generated grids (optional caching)

## Core Components

1. **Topic Management**: Categories like "Animals", "Science", "History"
2. **Word Selection**: Algorithm to pick words from chosen topic
3. **Grid Generation**: Place words intersecting on a grid
4. **Clue Generation**: Match words with appropriate clues
5. **UI Rendering**: Display interactive puzzle with input fields

## Key Algorithms Needed

- **Grid placement**: Find valid intersections between words
- **Backtracking**: Handle conflicts when placing words
- **Difficulty scaling**: Adjust grid size and word complexity

## Tech Stack Suggestions

- **Frontend**: React + CSS Grid for puzzle layout
- **Backend**: Node.js + Express or Python + Flask
- **Database**: PostgreSQL or MongoDB for word storage
- **Deployment**: Vercel/Netlify + Railway/Heroku

## Frontend Components & UI

**Main Page Layout**
```
Header: "Crossword Puzzle Generator"
Topic Selector: Dropdown with categories
Generate Button: "Create Puzzle"
Loading State: Spinner during generation
Puzzle Display: Grid + Clues
Actions: Reset, New Puzzle, Print
```

**Components:**
- `TopicSelector`: Multi-select topics
- `PuzzleGrid`: Interactive crossword grid
- `ClueList`: Numbered clues (Across/Down)
- `LoadingSpinner`: Generation feedback
- `PuzzleControls`: Reset/New/Difficulty buttons

**UI Flow:**
1. User selects topic(s)
2. Clicks generate → Loading state
3. Puzzle renders with empty grid
4. User fills in answers
5. Real-time validation feedback

## Backend API & Crossword Generation

**API Endpoints:**
```
GET /topics - List available topics
POST /generate - Generate puzzle
  Body: { topics: string[], difficulty: 'easy'|'medium'|'hard' }
  Response: { grid: Cell[][], clues: Clue[], metadata: {} }

GET /words/:topic - Get words for topic (admin)
POST /validate - Validate user answers
```

**Core Algorithm:**
1. **Word Selection**: Pick 8-15 words from chosen topics
2. **Grid Placement**: 
   - Start with longest word horizontally
   - Find intersections for perpendicular words
   - Use backtracking for conflicts
3. **Grid Optimization**: Minimize grid size, maximize word density
4. **Clue Matching**: Pair each word with appropriate clue

**Generation Logic:**
```javascript
class CrosswordGenerator {
  generatePuzzle(topics, difficulty) {
    const words = selectWords(topics, difficulty)
    const grid = createEmptyGrid()
    const placed = placeWords(words, grid)
    return { grid, clues: generateClues(placed) }
  }
}
```

## Data Storage & Word Management

**Database Schema:**
```sql
Topics: id, name, description
Words: id, word, length, difficulty_level, topic_id
Clues: id, word_id, clue_text, difficulty
Generated_Puzzles: id, grid_data, clues_data, created_at (optional caching)
```

**Word Collections by Topic:**
- **Animals**: DOG, ELEPHANT, TIGER, WHALE, BUTTERFLY
- **Science**: ATOM, GRAVITY, MOLECULE, PHOTON, CHEMISTRY  
- **Geography**: MOUNTAIN, OCEAN, DESERT, CONTINENT, RIVER
- **Technology**: COMPUTER, INTERNET, ALGORITHM, DATABASE, SOFTWARE

**Data Sources:**
- Curated word lists with quality clues
- Dictionary APIs for definitions
- Wikipedia API for topic-specific terms
- Manual curation for puzzle quality

**Storage Strategy:**
- PostgreSQL for structured word/clue data
- JSON columns for flexible puzzle metadata
- Indexing on topic_id and word_length for fast queries
- Caching layer (Redis) for frequent topic combinations

## Project Structure

```
crossword-app/
├── frontend/
│   ├── src/
│   │   ├── components/
│   │   │   ├── TopicSelector.jsx
│   │   │   ├── PuzzleGrid.jsx
│   │   │   ├── ClueList.jsx
│   │   │   └── LoadingSpinner.jsx
│   │   ├── hooks/
│   │   │   └── useCrossword.js
│   │   ├── utils/
│   │   │   └── gridHelpers.js
│   │   ├── styles/
│   │   │   └── puzzle.css
│   │   └── App.jsx
│   ├── package.json
│   └── vite.config.js
├── backend/
│   ├── src/
│   │   ├── controllers/
│   │   │   └── puzzleController.js
│   │   ├── services/
│   │   │   ├── crosswordGenerator.js
│   │   │   └── wordService.js
│   │   ├── models/
│   │   │   ├── Word.js
│   │   │   └── Topic.js
│   │   ├── routes/
│   │   │   └── api.js
│   │   └── app.js
│   ├── data/
│   │   └── word-lists/
│   ├── package.json
│   └── .env
└── database/
    ├── migrations/
    └── seeds/
```

**Tech Stack:**
- **Frontend**: React + Vite, CSS Grid, Axios
- **Backend**: Node.js + Express, CORS enabled
- **Database**: PostgreSQL with Prisma ORM
- **Development**: Nodemon, ESLint, Prettier

## Deployment & Hosting Strategy

**Development Environment:**
- Local PostgreSQL database
- Frontend: `npm run dev` (Vite dev server)
- Backend: `npm run dev` (Nodemon)
- Environment variables in `.env`

**Production Deployment:**
- **Frontend**: Vercel or Netlify (static hosting)
- **Backend**: Railway, Heroku, or DigitalOcean App Platform
- **Database**: PostgreSQL on Railway/Heroku/AWS RDS
- **Domain**: Custom domain with HTTPS

**CI/CD Pipeline:**
- GitHub Actions for automated testing
- Deploy on push to main branch
- Environment-specific configs (dev/staging/prod)

**Environment Variables:**
```
DATABASE_URL=postgresql://...
JWT_SECRET=...
CORS_ORIGIN=https://your-frontend-domain.com
PORT=3000
```

**Performance Considerations:**
- CDN for static assets
- Database connection pooling
- API rate limiting
- Puzzle result caching (Redis)

## Implementation Priority

1. **Phase 1**: Basic word placement algorithm and simple UI
2. **Phase 2**: Topic selection and word database
3. **Phase 3**: Interactive grid with validation
4. **Phase 4**: Polish UI/UX and deployment
5. **Phase 5**: Advanced features (difficulty levels, saving puzzles)