Building a Tic Tac Toe Game on Aptos with Move Language - Part1

Tic Tac Toe is a classic game that serves as a great example for demonstrating fundamental programming concepts. In this blog, we will learn how to implement a Tic Tac Toe game using the Move programming language on the Aptos blockchain platform. We will explore the structure, logic, and functionalities of the code, providing a thorough understanding of how to build decentralized applications (dApps) with Move.

Prerequisites for Understanding Tic Tac Toe Game Code in Move Language

Before diving into the code for implementing a Tic Tac Toe game using the Move language on the Aptos blockchain, it is essential to have some foundational knowledge and tools. Here are the prerequisites:

1. Basic Understanding of Blockchain Technology: Familiarity with how blockchain works, including concepts like distributed ledgers, smart contracts, and decentralized applications (dApps).

2. Introduction to Move Language: Move is a programming language designed by Facebook's Diem project (formerly Libra) for secure and efficient blockchain applications. Understanding its syntax and basic concepts is crucial. You should know about modules, structs, functions, and the type system in Move.

3. Familiarity with Aptos Blockchain: Aptos is a scalable and secure blockchain platform that uses the Move language. Knowing its architecture and how to deploy and interact with Move modules on Aptos will be beneficial.

4. Basic Programming Concepts: You should be comfortable with programming concepts such as variables, data types, functions, control structures, and error handling.

5. Development Environment: Setting up a development environment for Move and Aptos, including installing necessary tools like Move CLI, Aptos CLI, and any required dependencies.

The Tic Tac Toe game implemented here includes the following features:

1. Initializing a new game

2. Making a move

3. Checking for a winner

4. Emitting events for moves, wins, and draws

5. Resetting the game

6. Viewing the current game state

Basic Syntax Explanation of Complete Code:

                1. Module Declaration:

module tictactoe::game { ... }: This defines a module named game within the tictactoe namespace. A module in Move is similar to a class in other programming languages. It groups related functions and data structures.

                2. Imports:

use std::error;, use std::signer;, etc.: These lines import various standard libraries and functionalities that our module will use. For example, std::error helps handle errors, and std::vector allows us to use vectors (dynamic arrays).

               3. Constants:

const EINVALID_MOVE: u64 = 1;, etc.: These lines define constants used in our game. Constants are fixed values that don't change. Here, we're defining error codes and player identifiers. For example, EINVALID_MOVE is an error code for invalid moves, and PLAYER_X represents one player.

               4. Game Struct:

struct Game has key { ... }: This defines a data structure called Game. A struct in Move is similar to a class or a record in other languages. It groups related data together. The Game struct has three fields: board (a vector of 9 cells representing the Tic Tac Toe board), current_turn (indicating whose turn it is), and winner (indicating the winner).

               5. Event Structs:

MoveEvent has drop, store { ... }: This defines an event called MoveEvent. Events are special structures that get emitted during transactions to record what happened. MoveEvent stores the player who made a move and the position of the move.

Similarly, WinEvent is emitted when a player wins, and DrawEvent is emitted when the game ends in a draw.

               6. Function Declaration:

public entry fun init_game(account: &signer) { ... }: This defines a public entry function named init_game. Public entry functions can be called from outside the module. This function initializes a new game.

               7. Initializing the Game:

move_to(account, Game { ... });: This line creates a new Game struct and assigns it to the given account. vector::from_elem(EMPTY, 9) creates a vector of 9 empty cells, setting up the initial board. The current turn is set to PLAYER_X, and the winner is set to EMPTY.

This was part-1 of the blog, where the basics and setup were shown, in the next part complete code with the structure will be given.