Board Game Movement

Trying to figure out the best way to do this. What I'm trying to do is have a map with rooms.

r===r

||

 r  

Where the player can only click on the squares adjacent to them. I tried with raycasting, but that didn't work right. (It would let them go wherever.)I'd just like them to be limited to the adjacent squares, but can't figure this one out. I have the movement script, and I've tried grid move.

 using System.Collections;
 using UnityEngine;
  
 class GridMove : MonoBehaviour {
     private float moveSpeed = 3f;
     private float gridSize = 1f;
     private enum Orientation {
         Horizontal,
         Vertical
     };
     private Orientation gridOrientation = Orientation.Horizontal;
     private bool allowDiagonals = false;
     private bool correctDiagonalSpeed = true;
     private Vector2 input;
     private bool isMoving = false;
     private Vector3 startPosition;
     private Vector3 endPosition;
     private float t;
     private float factor;
  
     public void Update() {
         if (!isMoving) {
             input = new Vector2(Input.GetAxis("Horizontal"), Input.GetAxis("Vertical"));
             if (!allowDiagonals) {
                 if (Mathf.Abs(input.x) > Mathf.Abs(input.y)) {
                     input.y = 0;
                 } else {
                     input.x = 0;
                 }
             }
  
             if (input != Vector2.zero) {
                 StartCoroutine(move(transform));
             }
         }
     }
  
     public IEnumerator move(Transform transform) {
         isMoving = true;
         startPosition = transform.position;
         t = 0;
  
         if(gridOrientation == Orientation.Horizontal) {
             endPosition = new Vector3(startPosition.x + System.Math.Sign(input.x) * gridSize,
                 startPosition.y, startPosition.z + System.Math.Sign(input.y) * gridSize);
         } else {
             endPosition = new Vector3(startPosition.x + System.Math.Sign(input.x) * gridSize,
                 startPosition.y + System.Math.Sign(input.y) * gridSize, startPosition.z);
         }
  
         if(allowDiagonals && correctDiagonalSpeed && input.x != 0 && input.y != 0) {
             factor = 0.7071f;
         } else {
             factor = 1f;
         }
  
         while (t < 1f) {
             t += Time.deltaTime * (moveSpeed/gridSize) * factor;
             transform.position = Vector3.Lerp(startPosition, endPosition, t);
             yield return null;
         }
  
         isMoving = false;
         yield return 0;
     }
 }

But it won't keep them in the grid. The grid I have is:

 using UnityEngine;
 
 using System.Collections;
 
 
 
 public class Grid : MonoBehaviour
 {
     
     [ SerializeField ] private Transform _transform;
     
     [ SerializeField ] private Material _material;
     
     [ SerializeField ] private Vector2 _gridSize;
     
     [ SerializeField ] private int _rows;
     
     [ SerializeField ] private int _columns;
     
     
     
     void Start()
     {
         
         UpdateGrid();
         
     }
     
     
     
     public void UpdateGrid()
     {
         
         _transform.localScale = new Vector3( _gridSize.x, _gridSize.y, 1.0f );
         
         _material.SetTextureScale( "_MainTex", new Vector2( _columns, _rows ) );
         
     }
     
 }

With my grid texture on it. For some reason I can't keep them on the grid or make them move only to rooms that are actually there. I have triggers set up for the rooms, but everything seems to get ignored.

Any thoughts would be helpful.