Connect Four on Rails

Connect Four playable online or from the console.

Web Version

Play Connect Four on Heroku

You can swap the mode you are playing in any time using the select. This allow you to play as PvP for a few moves and then let the AI take over after your next turn.

Console Version

To play in the console:

• rails game:classic Player vs. Player
• rails game:easy Player vs. AI (Random)
• rails game:moderate Player vs. AI (Depth=2)
• rails game:hard Player vs. AI (Depth=3)

You can setup a board by sending in a list of play on the first move. For example, you can paste [1, 2, 1, 2, 1, 2, 1] into any move to play those moves.

Developer Guide

• Remember to run bundle
• Run test suite by rails test
• Start server by rails s

Interesting code:

• Board
• BasicAi
• ConnectFour Console
• Rake Game Task
• Connect Four Controller
• Connect Four in Vue.js
• Tests

Improvements

• Persist games to database
• Implement Alpha-Beta pruning to improve recursion costs
• Add scoring for 2 and 3 matching groups that have a possible four slot win or loss preferring the win
• DRY BasicAi .lookAhead() and .scoreBoard() methods
• Improve interface for Board.detect_win by creating a BoardState Class,
• potentially add some sort of Coordinates Class to remove some of the complexity of the Board class.
• Implement an AI based on Monte Carlo Tree Search

Known Bugs

• AI: hard AI occasionally misses obvious blocks (better scoring solves this)

Resources

• Wikipedia Connect Four
• MIT Lecture: Games, Minimax, and Alpha-Beta
• Minimax Algorithm
• Alpha-beta Pruning Variation
• Negamax Variation
• Connect Four Example and Tutorial in C++
• Connect Four in JavaScript
• Monte Carlo Tree Search

Project Goals

• Level 1: Build a playable game of Connect 4 with 2 players, a command line interface being fine. Should have player moves, win detection logic, tie detection, etc.
• Level 2: Implement a standard “AI” for the computer player. A standard computer opponent should block a human from winning when able to, but plays more ad hoc and does not operate with an advanced strategy.
• Level 3: Make it playable online (Heroku or similar) with a SPA web interface, games persisting to a database, etc.
• Boss Level (Bonus): the computer player's decision engine should have a setting for smarter vs standard opponent. The smarter version should employ any sort of intelligent strategy or look-ahead approach you choose, and be able to win most times (assuming it goes first and it’s not playing against a player with the same strategy), though it does not have to play mathematically perfectly.