TTT Bot Battle

Welcome to the Tic-Tac-Toe Bot Battle Tournament! You're going to build a bot that plays tic-tac-toe, and at the end of the session we'll pit all the bots against each other in a round-robin tournament on the big screen.

Don't worry about writing perfect code -- have fun, be creative, and name your bot something fun!

Getting Started

1. Clone the repo and create a branch:

http://bit.ly/3ZSwII5 (or https://github.com/site-mate/ttt-bot-battle)

Upload bot to https://drive.google.com/drive/folders/1hh3A-wmfCUXVDxmURWmYXV1VWuGteg9V?usp=drive_link when finished!

git checkout -b bot/your-name

2. Install dependencies:

npm install

3. Copy the starter bot into the candidates/ folder and give it your own name:

cp bots/starter-bot.js candidates/my-awesome-bot.js

4. Open your file and start making it smarter!

5. Test your bot:

node test.js ./candidates/my-awesome-bot.js

6. When you're happy with your bot, commit and push your branch, then open a PR to add your bot to the candidates/ folder:

git add candidates/my-awesome-bot.js
git commit -m "Add my-awesome-bot"
git push origin bot/your-name

Then open a Pull Request on GitHub -- your bot will be entered into the tournament once your PR is merged!

Your Bot

Your bot is a single function. It receives the board and which piece you're playing as, and returns the cell you want to place your piece in.

module.exports = function MyBotName(board, myPiece) {
  // board is a 3x3 array:
  // [
  //   ['X',  null, 'O' ],
  //   [null, 'X',  null],
  //   [null, null, null ]
  // ]
  //
  // myPiece is either 'X' or 'O'
  //
  // Return the cell you want to play:
  return { row: 0, col: 1 };
};

Board Layout

         col 0  |  col 1  |  col 2
        --------+---------+--------
row 0   (0,0)   |  (0,1)  |  (0,2)
        --------+---------+--------
row 1   (1,0)   |  (1,1)  |  (1,2)
        --------+---------+--------
row 2   (2,0)   |  (2,1)  |  (2,2)

• null means the cell is empty
• 'X' or 'O' means that piece is in the cell
• Rows and columns are numbered 0-2

Utility Helpers

We've provided some helpful functions you can import:

const { checkWinner, cloneBoard, wouldWin, opponent, getEmptyCells, printBoard } = require('../utils');

Function	What it does
checkWinner(board)	Returns 'X', 'O', or null
cloneBoard(board)	Returns a deep copy of the board (safe to mutate)
wouldWin(board, row, col, piece)	Returns true if placing piece at (row, col) would win
opponent(piece)	Returns the other piece ('X' -> 'O', 'O' -> 'X')
getEmptyCells(board)	Returns array of { row, col } for all empty cells
printBoard(board)	Pretty-prints the board to console (for debugging)

Testing Your Bot

# Test against all reference bots (shows win/loss/draw stats)
node test.js ./candidates/my-bot.js

# Watch the games play out visually, move by move
node test.js ./candidates/my-bot.js --watch

# Test against a specific bot
node test.js ./candidates/my-bot.js ./bots/starter-bot.js

# Watch a specific matchup
node test.js ./candidates/my-bot.js ./bots/starter-bot.js --watch

Your bot plays 10 games per opponent (5 as X, 5 as O) and you'll see your win/loss/draw record. Add --watch to see an animated board for each game so you can watch your bot's strategy in action.

Strategy Hints

Think about these questions as you improve your bot:

• Can you check if you're about to win and take that move?
• What if your opponent is about to win -- can you block them?
• Are some cells more valuable than others?
• What if you could simulate a move before making it to see what happens?

Rules

• Your bot must be synchronous (no async, no setTimeout, no network calls)
• No external npm packages -- just use the provided utils
• Don't modify any files outside your own bot file
• Your bot has a 1-second time limit per move -- if it takes longer, it forfeits
• If your bot returns an invalid move or throws an error, it forfeits that game
• Have fun!

Tournament Scoring

Result	Points
Win	3
Draw	1
Loss	0
Forfeit	0

Every bot plays every other bot twice -- once as X (going first) and once as O.