CLI Ruby Chess Game

This is the final project in the Ruby curriculum at The Odin Project.

Demo

1-minute demo game featuring Owen's Defense opening moves

Use of Design Patterns

The Odin Project's Discord community offered a book club for Design Patterns in Ruby. Every two weeks we would share code using each pattern and discuss them. Here is a brief summary of the 3 patterns that I implemented in this game:

Strategy: I implemented this pattern using the Board class as the context and the four Movement classes as different strategies. The Board changes its movement strategy to update the position of the piece(s) based on if the move is a basic move, en passant move, castling move, or pawn promotion move.

Factory: I implemented this pattern to create the different Movement classes needed for the above strategies. The Board passes a string to the Factory to know which type to create.

Observer: I implemented this pattern using the Board class as the subject and the Piece classes as the observers. When an instance of Piece is created, it becomes an observer of the Board instance. Every time a Piece moves in the Board, all of the pieces update their legal moves and captures. In addition, when a Piece is removed from the Board, that observer must also be removed.

Project Requirements

2-Player Game with Legal Moves: I wanted to create a similar UI as chess.com to visually display the opponent's previous piece, the active piece, and the legal moves/captures. Therefore, I needed to divide each turn into two different parts.

Save and Load Games: Players can save (or quit) a game at the beginning of every turn. Before a game starts, players have the choice to play a new game or load a saved game.

Tests: I wrote unit tests for incoming command methods, incoming query methods, and outgoing command methods. Most of the time, I wrote tests and the method in tandem. Occasionally, I used TDD when I wanted the test to guide the results. For example, I used TDD as I developed the methods that determined each piece's moves and captures.

Simple Computer Player (Optional): Since the white player always goes first and has a slightly higher advantage, I decided to have the computer player always be black to keep the game set-up simple. The computer player selects a piece with legal moves and/or captures.

How to Play

This chess game will look slightly different on other command line interfaces (CLI), such as repl.it or your computer. Not only will the colors vary, but the font size of my CLI is 24 points to increase the size of the unicode chess pieces.

Play Online

If you want to play this chess game without installing it on your computer, you can play it online. Just click the run button at the top of the page. It will take a few seconds to load the dependencies and then the game menu will appear.

Prerequisites

• ruby >= 2.6.5
• bundler >= 2.1.4

Installation

• Clone this repo (instructions)
• Navigate into this project's directory cd ruby_chess
• Run bundle install

To Play

• Run ruby lib/main.rb
• Play a 1-player or 2-player game (can save a game to load at a later time)

Running the tests

• To run the entire test suite, run rspec
• To run the tests for one file in the spec folder, run rspec spec/file_name.rb
• To run the tests for one file in the pieces folder, run rspec spec/pieces/file_name.rb
• To run the tests for one file in the movement folder, run rspec spec/movement/file_name.rb