Game Over Logic

After each move, we need to check if the game is over. The game ends when someone wins or it's a draw.

If/Else Statements:

Let you execute different code based on conditions.

Syntax:

if (condition) { ... } else if (anotherCondition) { ... } else { ... }

Example:

if (score > 100) { winner = true; } else { winner = false; }

For Our Game:

First, add a bool public gameOver; state variable to track if the game has ended.

Then update makeMove to check game state AFTER placing the piece:

• If checkWin() returns true → set gameOver = true;

• Else if checkDraw() returns true → set gameOver = true;

• Else → toggle turn with xTurn = !xTurn;

This ensures the turn only switches if the game continues.

Add game over logic with if/else

Requirements:

Declares bool public gameOver

Has if statement checking checkWin()

Sets gameOver = true when win

Has else if checking checkDraw()

Sets gameOver = true when draw

Has else clause

Toggles turn in else clause

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract TicTacToe {
    address public playerX;
    address public playerO;

    enum Cell { Empty, X, O }

    Cell[9] public board;

    bool public xTurn;

    function startGame(address _opponent) public {
        playerX = msg.sender;
        playerO = _opponent;
        xTurn = true;
    }

    function makeMove(uint _position) public {
        require(_position < 9, "Invalid position");
        require(board[_position] == Cell.Empty, "Cell already taken");
        require(xTurn ? msg.sender == playerX : msg.sender == playerO, "Not your turn");

        Cell piece = xTurn ? Cell.X : Cell.O;
        board[_position] = piece;

        xTurn = !xTurn;
    }

    function checkWin() private view returns (bool) {
        // Check rows
        for (uint i = 0; i < 3; i++) {
            if (board[i*3] != Cell.Empty &&
                board[i*3] == board[i*3+1] &&
                board[i*3] == board[i*3+2]) {
                return true;
            }
        }

        // Check columns
        for (uint i = 0; i < 3; i++) {
            if (board[i] != Cell.Empty &&
                board[i] == board[i+3] &&
                board[i] == board[i+6]) {
                return true;
            }
        }

        // Check diagonals
        if (board[0] != Cell.Empty &&
            board[0] == board[4] &&
            board[0] == board[8]) {
            return true;
        }

        if (board[2] != Cell.Empty &&
            board[2] == board[4] &&
            board[2] == board[6]) {
            return true;
        }

        return false;
    }

    function checkDraw() private view returns (bool) {
        for (uint i = 0; i < 9; i++) {
            if (board[i] == Cell.Empty) {
                return false;
            }
        }
        return true;
    }
}