Overview

This project explores game engine design inside the Linux kernel. The Connect Four module loads directly into a standard Linux kernel and exposes a character device, /dev/fourinarow, which manages game state and player input. The game can be played entirely from the terminal using simple read/write operations, without any user‑space program required.

Rules

For a quick refresher on Connect Four, here’s a short video overview. In this implementation, yellow always moves first.

Module Commands

RESET (R or Y): Resets the board and assigns the selected color to the player.

DROPC $: Drops a piece into column $. Only valid on the player's turn.

BOARD: Prints the current board state to /dev/fourinarow. Use cat to view it.

CTURN: Executes the computer’s move. Only valid when it is the computer’s turn.

User-Space Helper

Although the module can be controlled using standard terminal commands like echo and cat, the repository includes a helper program, connect4user, which simplifies interaction and provides a colorful UTF‑based board display.

Connect Four Engine

The module includes a lightweight AI engine designed to operate efficiently within kernel space. It uses no auxiliary data structures and relies on simple heuristics to evaluate moves.

How It Works

Due to kernel memory constraints, the AI evaluates all seven columns using a minimal scoring system. Moves are scored based on chain length, positional value, and immediate threats.

Winning moves receive extremely high scores to ensure they are always selected. The same logic is applied defensively: the AI simulates the opponent’s next move and blocks any high‑threat positions.

While effective for short‑term tactics, the AI does not perform multi‑move lookahead and can miss deeper strategic threats.