Move on a grid

RectangularMover.cs

/*
 * RectangularMover.cs
 * Purpose: Moves the object to the position where mouse-click points
 *          on a *rectangular* path. First on X, then on Z axis.
 *          Additional movement can not be issued until the current one finishes.
 * Uses coroutines for niceties.
 * Author: z_murc @ UnityAnswers
 */

using UnityEngine;
using System.Collections;

public class RectangularMover : MonoBehaviour {
  
	public float moveSpeed = 10f;
	Transform _transform;
	bool movementInProgress = false;
	float distanceThreshold = 0.01f;
	
	void Awake()
	{
		_transform = GetComponent<Transform>();
	}
	
	void Update () 
	{
		if (Input.GetMouseButtonDown(0) && !movementInProgress)
		{
			RaycastHit hit; 
			Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition); 
			if(Physics.Raycast(ray, out hit, Mathf.Infinity))
			{
				if (hit.collider.tag == "Floor")
				{
					StartCoroutine(RectMove(hit.point));
				}
			}
		}
	}
	
	IEnumerator RectMove(Vector3 destination)
	{
		// this will be true in the following Updates, until this whole coroutine finishes
		movementInProgress = true;
		
		// 0. the movement vector
		Vector3 moveVector = destination - _transform.position;
		Vector3 target;
		
		// 1. move on X
		target = _transform.position + new Vector3(moveVector.x, 0, 0);
		yield return StartCoroutine(MoveTo(target));
		
		// 2. when finished, move on Z
		target = _transform.position + new Vector3(0, 0, moveVector.z);
		yield return StartCoroutine(MoveTo(target));
		
		movementInProgress = false;
	}
	
	IEnumerator MoveTo(Vector3 destination)
	{
		while (true)
		{
			_transform.position = Vector3.MoveTowards(_transform.position, destination, 
			                                          moveSpeed * Time.deltaTime);
			if (Vector3.Distance(_transform.position, destination) < distanceThreshold)
				yield break;
			else
				yield return null;
		}
	}
}