MovePlate.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class MovePlate : MonoBehaviour
{
    public GameObject controller;

    GameObject reference = null;

    // Board position, not world position
    int matrixX;
    int matrixY;

    // false: movement, true: attack
    public bool attack = false;

    public void Start()
    {
        if (attack){
            // Change to red
            gameObject.GetComponent<SpriteRenderer>().color = new Color(1.0f, 0.0f, 0.0f, 1.0f);
        }

    }

    public void OnMouseUp()
    {
        controller = GameObject.FindGameObjectWithTag("GameController");

        if (attack)
        {
            GameObject cp = controller.GetComponent<Game>().GetPosition(matrixX, matrixY);

            if (cp.name == "white_king") controller.GetComponent<Game>().Winner("black");
            if (cp.name == "black_king") controller.GetComponent<Game>().Winner("white");

            Destroy(cp);
        }

        // Clear old postion after moving chess piece
        controller.GetComponent<Game>().SetPositionEmpty(reference.GetComponent<Chessman>().GetXBoard(), reference.GetComponent<Chessman>().GetYBoard());

        // Set new position for chess piece after moving
        reference.GetComponent<Chessman>().SetXBoard(matrixX);
        reference.GetComponent<Chessman>().SetYBoard(matrixY);
        reference.GetComponent<Chessman>().SetCoords();

        controller.GetComponent<Game>().SetPosition(reference);

        controller.GetComponent<Game>().NextTurn();

        // Destroy move plate
        reference.GetComponent<Chessman>().DestroyMovePlates();

        controller.GetComponent<Game>().UpdateBoardState();
    }

    public void SetCoords(int x, int y)
    {
        matrixX = x;
        matrixY = y;
    }

    // Setter and Getter
    public void SetReference(GameObject obj){
        reference = obj;
    }

    public GameObject GetReference(){
        return reference;
    }
}