grid.cs

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

public class MobSpawner : MonoBehaviour
{ 
    public class Trap
    {
        private static int ordinal = 0;
        
        public Color Color { get; }
        public int Ordinal { get; }
        
        public Trap()
        {
            Color = Random.ColorHSV();
            Ordinal = ordinal++;
        }
    }

    List<Trap> traps;
    List<Trap> inventory;

    public class GridData : MonoBehaviour
    {
        public Trap Trap { get; set; }
    }

    const int SLOTS = 5;
    
    // Start is called before the first frame update
    void Start()
    {
        traps = new List<Trap>();
        inventory = new List<Trap>();

        /* populate random traps */
        for (int i = 0; i < 16; ++i)
            traps.Add(new Trap());
        
        /* generate grid */
        for (int i = 0; i < 4; ++i)
            for (int j = 0; j < 4; ++j)
            {
                GameObject element = GameObject.CreatePrimitive(PrimitiveType.Quad);
                element.transform.position = new Vector3(-2.0f + i * 0.6f, -2.0f + j * 0.6f, 0.0f);
                element.transform.localScale = new Vector3(0.5f, 0.5f, 0.5f);
                element.GetComponent<Renderer>().material.color = traps[j + i * 4].Color;
                element.AddComponent(typeof(GridData));
                element.GetComponent<GridData>().Trap = traps[j + i * 4];
            }
    }


    // Update is called once per frame
    void Update()
    {
        if (Input.GetMouseButtonDown(0))
        {
            RaycastHit raycastHit;
            Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
            if (Physics.Raycast(ray, out raycastHit, 100f))
            {
                if (raycastHit.transform != null)
                {
                    GameObject element = raycastHit.transform.gameObject;
                    Trap trap = element.GetComponent<MobSpawner.GridData>().Trap;

                    if (trap != null)
                    {
                        if (inventory.Count < SLOTS && !inventory.Contains(trap))
                        {
                            Debug.Log("Adding: " + trap.Ordinal);
                            inventory.Add(trap);
                            element.transform.Rotate(new Vector3(0.0f, 0.0f, 45.0f));
                        }
                        else if (inventory.Contains(trap))
                        {
                            Debug.Log("Removing: " + trap.Ordinal);
                            inventory.Remove(trap);
                            element.transform.Rotate(new Vector3(0.0f, 0.0f, -45.0f));
                        }

                        Debug.Log("Inventory size: " + inventory.Count);
                    }
                }
            }
        }
    }
}