# TicTacToe-v0

### Overview

TicTacToe is a classic two-player strategy game played on a 3x3 grid. The goal is to be the first player to align three of your marks, either `X` or `O`, horizontally, vertically, or diagonally. This simple yet elegant game tests players’ ability to anticipate, block, and plan moves ahead, making it a suitable environment for evaluating reasoning, prediction, and opponent modeling in large language models (LLMs).

---

### Gameplay

* **Players:** 2
* **Symbols:** `X` and `O`
* **Objective:** Form a line of three of your symbols before your opponent.
* **Board Layout:**

  ```
   0 | 1 | 2
  ---+---+---
   3 | 4 | 5
  ---+---+---
   6 | 7 | 8
  ```

Players take turns selecting a cell by its index (0–8). The environment automatically validates moves and announces wins, losses, or draws.

---

### Environment Details

* **Environment Name:** `TicTacToe-v0`
* **Number of Players:** 2
* **Observation Type:** Text-based description of board state and game messages
* **Action Type:** Integer index (0–8)
* **Winning Condition:** Three identical symbols in a row, column, or diagonal
* **Termination:** When a player wins or all cells are filled (draw)

---

### LLM Evaluation Purpose

TicTacToe serves as a benchmark for:

* **Strategic reasoning:** planning moves and anticipating outcomes
* **Opponent modeling:** predicting and countering adversarial play
* **Deterministic decision-making:** consistent performance under clear rules

It is also a good starting environment for reinforcement learning or self-play fine-tuning of small or large language models.