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# Solidity Tic Tac Toe Project **Feature ID:** feature-hy5l98td ## Clarification Responses ### What specific problem does this feature solve? This feature solves the problem of creating verifiable, tamper-proof gaming experiences on blockchain. It demonstrates how traditional games can be implemented in a decentralized manner where the game state and rules are enforced by smart contracts rather than a central server, ensuring fair play and transparent outcomes. ### Who are the target users for this feature? The target users are: 1) Blockchain enthusiasts who want to experience decentralized gaming 2) Ethereum developers learning how to implement game logic in smart contracts 3) Educational platforms teaching blockchain concepts through familiar games 4) Players interested in crypto-gaming who want to try simple blockchain games with potential for token rewards ### What are the key requirements for this feature? Key requirements include: 1) A Solidity smart contract that implements the complete Tic Tac Toe game logic 2) Functions for player registration and turn management 3) Win condition detection and game state verification 4) Prevention of illegal moves and proper handling of drawn games 5) Option for players to wager ETH on game outcomes 6) Events that can be used by a frontend to track game progress 7) Gas-efficient implementation to minimize transaction costs ### What are the technical constraints or considerations? Technical constraints include: 1) Gas optimization is critical - each move costs ETH to execute 2) The contract must be compatible with Solidity 0.8.x and deployable to Ethereum and compatible chains like Polygon 3) State management must be efficient as blockchain storage is expensive 4) Proper access control is needed to ensure only valid players can make moves in their own games 5) Time constraints should be considered to prevent abandoned games 6) Input validation is crucial to prevent exploits or illegal game states 7) No external dependencies should be required beyond standard Solidity libraries ### How will we measure the success of this feature? Success will be measured by: 1) Successful deployment of the contract to a testnet with verified gameplay 2) Completion of full games without errors or invalid states 3) Gas usage below 200,000 gas per move 4) Proper detection of all win conditions and draws 5) Correct handling of wagers and payouts 6) Successful integration with a basic web frontend for demonstration 7) Security audit passing without critical vulnerabilities 8) Documentation that allows developers to understand and interact with the contract ### Are there any dependencies on other features or systems? Dependencies include: 1) Ethereum or compatible blockchain network for deployment 2) Solidity compiler version 0.8.x 3) Hardhat or Truffle for development, testing and deployment 4) Ethers.js or Web3.js for frontend integration 5) MetaMask or similar Web3 provider for user interaction 6) A basic frontend application (HTML/JS/CSS) for user interface, though this could be developed separately 7) OpenZeppelin contracts for secure implementation patterns (optional) ### What are the potential risks or challenges in implementing this feature? The potential risks and challenges include: 1) High gas costs making gameplay expensive if not optimized 2) Smart contract security vulnerabilities like reentrancy attacks or integer overflows 3) Poor user experience due to blockchain transaction delays 4) Abandoned games if players stop participating 5) Complexity in handling edge cases like ties or unexpected termination 6) Difficulties in upgrading the contract if bugs are found since blockchain code is immutable 7) Ensuring fairness in the game mechanics while maintaining decentralization 8) Testing challenges due to the distributed nature of blockchain applications ## Development Phases ### Phase 1: Smart Contract Development **Status**: In Progress **Description**: Develop the core Solidity smart contract for the Tic Tac Toe game, including game logic, state management, and event emission. **Tasks**: - Set up Hardhat development environment with Solidity 0.8.x - Implement game board representation and state management - Implement player registration and game creation functionality - Implement move validation and game state updates - Implement win condition detection and game completion logic ### Phase 2: Testing and Optimization **Description**: Write test cases, optimize gas usage, and ensure security of the Tic Tac Toe contract. **Tasks**: - Write unit tests for all game functionality - Perform gas optimization for core game functions - Conduct security review and implement safeguards ### Phase 3: Deployment and Documentation **Description**: Deploy the contract to testnets and create comprehensive documentation for developers and users. **Tasks**: - Deploy contract to Ethereum testnet (Goerli/Sepolia) - Create technical documentation with API references - Create a demo frontend for interacting with the contract ## Product Requirements Document ### 1. Introduction #### 1.1 Purpose This document outlines the requirements and specifications for a decentralized Tic Tac Toe game implemented as a Solidity smart contract on the Ethereum blockchain. The goal is to create a fully functional, gas-efficient, and secure implementation that demonstrates how traditional games can be implemented in a trustless, decentralized environment. #### 1.2 Scope The scope of this product includes the smart contract implementation of Tic Tac Toe, including game creation, player management, game logic, win condition detection, and wagering functionality. A basic web frontend for interacting with the contract will be developed as part of the demonstration but is not the primary focus of this PRD. #### 1.3 Background Blockchain games represent a growing segment of the web3 ecosystem, offering new possibilities for transparent and verifiable gameplay. Tic Tac Toe, as a simple yet widely understood game, provides an excellent introduction to smart contract gaming concepts while being straightforward enough to implement efficiently on-chain. ### 2. Product Overview #### 2.1 Product Description A decentralized Tic Tac Toe game built on Ethereum that allows two players to compete against each other with all game actions and state changes recorded on the blockchain. Players can create games, join existing games, make moves, and potentially wager ETH on the outcome. #### 2.2 Target Users - Blockchain enthusiasts interested in decentralized applications - Ethereum developers learning smart contract development - Educational platforms teaching blockchain concepts - Casual players interested in crypto gaming experiences ### 3. Functional Requirements #### 3.1 Game Creation and Setup - Users must be able to create a new game, becoming player 1 (X) - Users must be able to join an existing open game as player 2 (O) - Game creators must be able to specify whether ETH wagering is enabled - If wagering is enabled, both players must contribute the same amount of ETH to participate #### 3.2 Gameplay Mechanics - The game board must be represented as a 3x3 grid - Players must take turns making moves, with player 1 (X) always going first - The contract must validate moves to ensure they are made: - By the correct player - On a valid, empty position on the board - During an active game - The contract must prevent players from making moves when it's not their turn - The contract must update and store the game state after each valid move #### 3.3 Win Conditions and Game Completion - The contract must detect win conditions: 3 in a row horizontally, vertically, or diagonally - The contract must detect draw conditions when all positions are filled with no winner - When a game is completed, the contract must: - Record the winner (or draw) - Prevent further moves - Distribute any wagered ETH to the winner (or refund in case of a draw) #### 3.4 Event Emission - The contract must emit events for: - Game creation - Player joining a game - Each valid move made - Game completion (win/draw) - ETH distribution if wagering is enabled ### 4. Non-Functional Requirements #### 4.1 Performance and Optimization - Gas usage for moves should be below 200,000 gas - The contract should minimize on-chain storage to reduce gas costs - The game logic should be optimized for minimal computational complexity #### 4.2 Security - The contract must implement proper access controls - Input validation must be comprehensive to prevent unexpected game states - The contract should be resistant to common smart contract vulnerabilities - The contract must handle ETH transfers securely if wagering is enabled #### 4.3 Compatibility - The contract must be compatible with Solidity 0.8.x - The contract must be deployable to Ethereum mainnet and testnets - The contract should work with standard Web3 providers like MetaMask ### 5. Technical Specifications #### 5.1 Smart Contract Architecture - `TicTacToe.sol`: Main contract implementing the game logic - Data structures: - Game struct containing board state, player addresses, current turn, game status, and wager information - Mapping from game ID to Game struct for multi-game support - Key functions: - `createGame()`: Create a new game instance - `joinGame(uint gameId)`: Join an existing game - `makeMove(uint gameId, uint8 x, uint8 y)`: Make a move on the board - `getGameState(uint gameId)`: Return the current state of a specific game #### 5.2 Development Environment - Hardhat for development, testing, and deployment - Solidity 0.8.x as the smart contract language - Ethers.js for frontend integration - OpenZeppelin contracts for security patterns (optional) ### 6. User Interface (Frontend) While the frontend is not the primary focus, a basic web interface should be developed to demonstrate interaction with the smart contract: #### 6.1 Key Frontend Features - Connect wallet functionality - Create new game / Join existing game options - Visual representation of the game board - Move selection interface - Game status display - Transaction status and confirmation ### 7. Testing Strategy #### 7.1 Unit Testing - Test all contract functions in isolation - Verify win condition logic covers all possible winning configurations - Test error conditions and invalid inputs #### 7.2 Integration Testing - Test full game scenarios from creation to completion - Test wagering functionality if implemented - Verify correct event emission #### 7.3 Security Testing - Review for common smart contract vulnerabilities - Test for correct access control enforcement - Verify proper handling of ETH transfers ### 8. Milestones and Implementation Plan The implementation will be organized into three main phases: #### 8.1 Phase 1: Smart Contract Development - Set up development environment - Implement core game logic and state management - Build player registration and turn management - Create win condition detection #### 8.2 Phase 2: Testing and Optimization - Develop comprehensive test suite - Optimize for gas efficiency - Conduct security review #### 8.3 Phase 3: Deployment and Documentation - Deploy to Ethereum testnet - Create technical documentation - Develop demo frontend ## Implementation Plan ### 1. Environment Setup #### 1.1 Development Environment - Set up a Hardhat project for Solidity development - Configure for Solidity version 0.8.17 - Install necessary dependencies: - `@openzeppelin/contracts` (optional, for security patterns) - `@nomiclabs/hardhat-ethers` for testing - `@nomiclabs/hardhat-waffle` for testing - Configure testing environment with Hardhat #### 1.2 Project Structure ``` /contracts /TicTacToe.sol /test /TicTacToe.test.js /scripts /deploy.js /frontend (optional for demo) /src /components /utils hardhat.config.js package.json README.md ``` ### 2. Smart Contract Development #### 2.1 Contract Data Structures Define the core data structures: ```solidity // Game status enum enum GameStatus { OPEN, IN_PROGRESS, WINNER_X, WINNER_O, DRAW } // Game struct to track game state struct Game { address playerX; // Player 1 (X) address playerO; // Player 2 (O) address currentTurn; // Whose turn it is uint8[9] board; // Board state (0=empty, 1=X, 2=O) GameStatus status; // Current game status uint256 wagerAmount; // ETH wagered (if any) uint256 createdAt; // Timestamp for game creation } // Mapping to track all games mapping(uint256 => Game) public games; uint256 public gameCount; ``` #### 2.2 Core Game Functions Implement these core functions: 1. **Game Creation** ```solidity function createGame(bool withWager) external payable returns (uint256 gameId) { // Input validation for wager // Create new game with player X as msg.sender // Set initial game state // Emit GameCreated event } ``` 2. **Joining a Game** ```solidity function joinGame(uint256 gameId) external payable { // Validate game exists and is open // Validate wager amount if needed // Set player O as msg.sender // Update game status to IN_PROGRESS // Emit PlayerJoined event } ``` 3. **Making a Move** ```solidity function makeMove(uint256 gameId, uint8 position) external { // Validate game state and player turn // Validate move is legal (position is in range and empty) // Update board state // Check for win conditions // Update game status if game is complete // Handle ETH distribution if game is complete and has wager // Emit MoveExecuted event } ``` 4. **Game State Retrieval** ```solidity function getGameState(uint256 gameId) external view returns ( address playerX, address playerO, address currentTurn, uint8[9] memory board, GameStatus status ) { // Return all relevant game state information } ``` #### 2.3 Win Condition Detection Implement an efficient algorithm to check for wins: ```solidity function checkWinner(uint8[9] memory board) internal pure returns (bool hasWinner, uint8 winner) { // Check rows, columns, and diagonals for 3 in a row // Return winner (1 for X, 2 for O) if found // Otherwise return no winner } ``` #### 2.4 ETH Handling Handle wagering functionality: ```solidity function _distributeWinnings(Game storage game) internal { // Send ETH to winner or refund in case of draw // Handle potential transfer failures safely } ``` ### 3. Testing Strategy #### 3.1 Unit Tests Write tests for: - Game creation with and without wager - Joining games - Making valid and invalid moves - Win detection for all winning positions - Draw detection - ETH distribution logic #### 3.2 Gas Optimization - Use uint8 for board positions (0, 1, 2) - Optimize win condition checking - Minimize storage operations - Consider using bit manipulation for board state ### 4. Deployment and Documentation #### 4.1 Deployment Scripts Create scripts for: - Testnet deployment - Local testing deployment #### 4.2 Documentation Document: - Contract functions and parameters - Game mechanics and flow - Integration guidelines for frontends - Examples of interaction using ethers.js #### 4.3 Frontend Demo (Optional) If time permits, create a basic React frontend: - Wallet connection - Game creation interface - Game board visualization - Move submission ### 5. Implementation Timeline #### Week 1: Smart Contract Development - Day 1-2: Set up environment and implement data structures - Day 3-4: Implement core game functions - Day 5: Implement win condition detection and ETH handling #### Week 2: Testing and Optimization - Day 1-2: Write comprehensive tests - Day 3-4: Gas optimization - Day 5: Security review #### Week 3: Deployment and Documentation - Day 1-2: Create deployment scripts and deploy to testnet - Day 3-4: Write documentation - Day 5: (Optional) Create basic frontend demo