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I recently rediscovered one of my earliest projects, the "Dragons vs Unicorns" game series, and decided to apply my artificial intelligence expertise to enhance it. This post serves as a continuation of the series, with minimal alterations to the existing HTML structure and core JavaScript logic.

In this final installment, we will explore the integration of an AI opponent into our interactive game, which was originally developed using HTML, CSS, and JavaScript. The focus of this update is the implementation of a challenging computer player utilizing the minimax algorithm, thus adding a sophisticated twist to the traditional gameplay.

This post will provide a detailed walkthrough of the AI integration process, demonstrating how we can elevate a simple two-player game into a more complex and engaging single-player experience. We'll examine the step-by-step process of incorporating AI decision-making into our existing game framework.

You can play the live version here: https://pedropcamellon.github.io/tic-tac-toe/; or you can check the repo here: https://github.com/pedropcamellon/tic-tac-toe.

Game Initialization and Flow

The game will initialize as before, with the board set up and ready for play. Here's how the enhanced gameplay will unfold:

1. Game Start: The game begins with an empty 3x3 grid, just as in our original version.
2. Human's First Move: The human player, represented by the Unicorn, always makes the first move. They can click on any empty cell to place their symbol.
3. AI's Turn: After the human player's move, control transitions to the AI (the Dragon). Here's where our new implementation comes into play:
   • The game will display a brief "thinking" state, simulating the AI's decision-making process.
   • Our AI, powered by the minimax algorithm, will evaluate the board state and determine the optimal move.
   • After a short delay (to enhance user experience), the AI will make its move by placing the Dragon symbol in its chosen cell.
4. Alternating Turns: The game will continue to alternate between the human player and the AI until a win or draw condition is met.
5. Game End: The game concludes when either player achieves a winning combination or when the board is full (resulting in a draw).

For the AI implementation, we'll focus on the essential elements from the previous sections:

1. Game Variables:
   • We retain the AI_PLAYER and HUMAN_PLAYER constants, which define the Dragon as the AI and the Unicorn as the human player.
   • The cells NodeList is crucial for accessing the game board state.
2. Utility Functions:
   • placeBeastImg: Used to place the AI's move on the board.
   • checkWin: Essential for evaluating game states in the AI algorithm.
   • isDraw: Needed to check for draw conditions in the AI logic.
3. Event Handler:
   • The handleCellClick function now includes a call to handleAITurn() after the human player's move, which will be the entry point for our AI logic.

These elements provide the foundation for implementing the AI player. The AI will utilize the existing game state representation and win-checking mechanisms while introducing new functions for decision-making using the minimax algorithm.

In the following sections, we'll dive into the specifics of implementing the AI logic, focusing on the minimax algorithm and how it integrates with our existing game structure. This enhancement will transform our two-player game into an engaging single-player experience, challenging human players with a formidable AI opponent. Let's proceed to examine the AI implementation in detail.

Start the AI turn

The handleAITurn function serves as the core of our AI player's decision-making process in the Dragons vs Unicorns game. When it's the AI's turn, this function orchestrates a series of critical actions. First, it calls the findBestMove function, which utilizes the minimax algorithm to determine the optimal cell for the AI's next move. Once the best move is identified, the function places the AI's symbol (the Dragon) on the chosen cell using the placeBeastImg function. After making its move, the AI checks for a win condition or a draw using the checkWin and isDraw functions respectively. If either condition is met, the game ends accordingly. If the game continues, the function switches the current player back to the human player (the Unicorn) and updates the game status display. This function encapsulates the AI's turn logic, ensuring a smooth transition between human and AI moves while maintaining the game's rules and flow.