if (Input.GetKeyDown (KeyCode.Mouse0) && isDeadFreeze) {
            RaycastHit hit;
            Ray ray = mainCamera.ScreenPointToRay (new Vector3 (Input.mousePosition.x, Input.mousePosition.y, Input.mousePosition.z));
            if (Physics.Raycast (ray, out hit)) {
                playSound (clickSound);
                if (hit.collider.tag == "Tiles" && hit.collider.transform.position.z == -0.89f) {
                    hit.collider.transform.position = new Vector3 (hit.collider.transform.position.x, hit.collider.transform.position.y, -1.36f);
                    numberOfActiveTiles++;
                    checkNumber ();
                } else if (hit.collider.tag == "Tiles" && hit.collider.transform.position.z == -1.36f) {
                    hit.collider.transform.position = new Vector3 (hit.collider.transform.position.x, hit.collider.transform.position.y, -0.89f);
                    numberOfActiveTiles--;
                }
            }
        }