low level design

Designing Tic-Tac-Toe: A Low-Level Design Walkthrough

A complete object-oriented design for Tic-Tac-Toe — a playable board, the full class model (players, board, pluggable rules), an O(1) win check, a codeable interface you can implement, and the patterns that scale it to N×N, K-in-a-row, and bots.