This guide will walk you through the process of setting up the game board, creating chess pieces, and implementing basic game logic, including an AI opponent that can play against you.

1

Prerequisites

To go through this tutorial, you should have the following:

  • A new Unity project with Coplay installed.

When making a new project, make sure to select the 3D Built-In Render Pipeline template as this tutorial uses assets build with that rendering pipeline. This is required for the chess assets you’ll be using. You can use the HDRP or URP templates, but you will need to adjust the materials and shaders accordingly.

2

Configure your Coplay settings

  • Open the Coplay settings window by going to Coplay > Toggle Window in the Unity menu or pressing ⌘ + G or CTRL + G depending on whether you’re on Mac or PC.
  • Make sure the Auto-approve option is checked.
  • Set the Model to claude-4-sonnet (feel free to play around with other models — we have generally found the best performance with this one).
3

Import Your Chess Assets

  • Download the chess asset pack from the Unity Asset Store.
  • Navigate to Window > My Assets and import the downloaded package into your Unity project.
  • You should now see a folder named Chess Pieces in your project window.

Make sure to uncheck the Blender.zip and Chess Demo.Unity files when importing the package, as they are not needed for this tutorial.

4

Write a prompt telling Coplay what to do

This is the fun part. Use the prompt below as a starting point but feel free to modify it to your liking once you have a working game.

This prompt is going to change the following:

  • Each game piece controlling possible actions
  • A game manager that initializes the board with appropriate layout and manages game state
  • Mouse input controller using Unity’s Input System with raycast detection for piece selection,
  • AI opponent with minimax algorithm and adjustable difficulty levels.
Prompt Instructions

## Goal
Create a chess game using assets from `Assets/Chess Set` directory.

## Development Plan

### 1. Piece Scripts (`Scripts/Pieces/`)
- Create individual scripts for each chess piece type (Pawn, Rook, Knight, Bishop, Queen, King)
- Each script controls movement rules and logic for that piece type
- Use inheritance with a base `ChessPiece` class for common functionality

### 2. Game Manager Script and Component
- Create `GameManager.cs` to handle core game logic
- Initialize board with pieces in starting positions using:
- Prefabs from `Assets/Chess Set/Prefabs/`
- Scripts from `Scripts/Pieces/`
- Assign the prefabs via the Inspector
- Manage turn system and game state

### 3. Mouse Input Controller Script and Component
- Use the new Unity Input System
- Use raycast to detect piece/square selection
- Visual feedback for selected pieces and valid moves
- Deselection logic (same piece click or empty square)
- Clicking on a valid square moves the piece to that square
- Change piece material to indicate selection
- Add highlight effect to valid move squares

### 4. AI Opponent Script and Component
- Create AI script that makes legal moves
- Implement basic chess strategies
- Include adjustable difficulty levels as script variables
- Use minimax algorithm or similar for move selection
- Use raycasting to detect piece collision.
- The AI should collide with opposing pieces to take them whenever possible.
- IMPORTANT: If a king piece is captured, the game should end immediately.

## Technical Requirements

### Camera Setup
- Position camera x = 0, y = 40, z = -40
- Set camera rotation to 50 degrees for optimal board view

### Piece Positioning
**Important**: 
- Calculate piece positions using board square count and Chess Board Play Surface dimensions
- The Chess Board Play Surface of the board is 48x48 units and there are 64 squares, so each square is 6x6 units.
- **Rotations**:
- All pieces: X-axis = -90° (face upward)
- White pieces: Y-axis = -90°
- Black pieces: Y-axis = 90°
- Chess Board: X-axis = -90° (face upward)
- IMPORTANT: Set Y position = 1 for pawns
- IMPORTANT: Set Y position = 0 for all other pieces
- IMPORTANT: Add box colliders to all pieces with size X = 0.035 Y = 0.03 Z = 0.05

### Best Practices
- Initialize the board and all pieces in the `GameManager` script.
- Use `[SerializeField]` for inspector variables
- Save progress regularly during development
- IMPORTANT: DO not use the Unity Editor to add the board and pieces to the scene.
- IMPORTANT: Add a `BoardClickPlane` GameObject at Y position = 0 and scale of X = 4.8 Y = 1 and Z = 4.8.
- IMPORTANT: Assign a MeshCollider with Mesh value of Plane to the `BoardClickPlane` GameObject.
- IMPORTANT: Add a MeshFilter with Mesh value of Plane to the `BoardClickPlane` GameObject.
- IMPORTANT: Assign the `BoardClickPlane` GameObject a tag called `BoardClickPlane` to detect clicks on the board.
- IMPORTANT: Verify the correct action map is active (usually "UI" for mouse clicks)
- IMPORTANT: Check if Input Actions asset is assigned correctly
- IMPORTANT: Use direct mouse input for reliable clicking - e.g. Vector2 mousePosition = Mouse.current.position.ReadValue();

## Debugging Tips
### 1. Check Unity Console Logs
- Look for `MissingMethodException: Method 'OnClick' not found` errors
- Check for Input System related errors
- Enable debug logging in MouseInputController to trace click detection

### 2. Verify Input System Configuration
- Ensure PlayerInput component is properly configured
- Check if Input Actions asset is assigned correctly
- Verify the correct action map is active (usually "UI" for mouse clicks)

### 3. Test Raycast Detection
Add debug logging to MouseInputController to verify:
- Mouse clicks are detected
- Raycasts hit pieces correctly
- Raycasts hit board/empty squares

## Implementation Order
1. Set up the camera
2. Create base piece class and individual piece scripts
3. Set up GameManager with board initialization and BoardClickPlane
4. Create mouse input controller for piece selection and movement
5. Implement piece positioning and rotation system
6. Create AI opponent with difficulty settings
5

Run the prompt

  • Copy the prompt above and paste it into the Coplay chat window.
  • Press Enter to send the prompt to Coplay.
  • Wait for Coplay to process the request and generate your chess game.
6

Go get a coffee

You’ve earned it. Coplay’s got it from here.

7

Check in on Coplay's progress

  • After a few minutes, check the Coplay chat window to see the progress of the chess game creation.
  • Coplay will provide updates on the game setup but will stop every 20 actions to ask for your approval. This is expected and default behavior to ensure you have control over the changes being made to your project.
  • If Coplay asks for approval just click the Approve button to continue.
  • If you want to make changes to the game, you can stop Coplay by pressing Shift + ⌫ or clicking the Stop Thinking button in the Coplay chat window.
8

Play the Game

  • Once Coplay has finished creating the chess game, you can play it by clicking the Play button in the Unity Editor.
  • Follow the on-screen instructions to start playing against the AI opponent.
  • If you want to change the AI difficulty, you can do so by modifying the AI script in the Assets/Chess Pieces/Scripts folder.
9

Share Your Game with Us!

We would love to see what you have created! Share your chess game with us on social media and tag us! Even better, share it in the Coplay Discord community.

10

Take Your Game to the Next Level!

Now that you have a basic chess game, consider enhancing it with additional features: