seipy/tic-tac-toe-gd3

A VERY simple tic-tac-toe game using Godot 3.0 beta-1

Behold! Tic Tac Toe!!

This is a VERY simple tic-tac-toe game using Godot 3.1. I wrote this some time ago and recently refined it after Godot 3.1 was release. This game does not use a _process loop. Instead it's entirely event driven by the button clicks. This game is single player vs computer.

Youtube overview

I have a Youtube overview here: https://youtu.be/2yIAXi9c2ag

History

When I interview software engineers for a new job, I sometimes ask them to write the logic for a tic tac toe game, assuming the UI is developed for them. Their task is to represent the game state and check for the win / lose / tie conditions - if they knock that out of the park we start talking about ways to code the AI, and computational complexity if we decided to change the game to 4 in a row or 5 in a row. I thought it might be fun to do the exercise with Godot, and thus this project was born.

Scoring

The board uses a simple array of buttons each of which holds a value initialized to zero. I use the constants 1 and 10 to represent the player values X and O. Setting the board values to 1 or 10 based upon which player selects a position makes scoring and AI pretty easy:

onready var board = [
            [$TicTacButton1, $TicTacButton2, $TicTacButton3],
            [$TicTacButton4, $TicTacButton5, $TicTacButton6],
            [$TicTacButton7, $TicTacButton8, $TicTacButton9], 
            ]
.
.

# We use these player values for two purposes
# To distiguish the "activePlayer", and to make
# scoring easy.
const X = 1
const O = 10  # The computer

To check for win conditions we can simply sum the rows, cols or diagonals. If the sum is 3 * X, X wins .. if the sum is 3 * O, then of course O wins.

AI logic is as follows:

• Check for a winning move (do any row,col,diag sums == 20 or 2*O)
• If no winning move, check for a block (prevent the player from winning if they have a score of 2 in a row, column or diagonal.
• If neither of the above, just select a random square.