Ошибка с переменной класса Transform

using UnityEngine;
using System.Collections;
 
public class charactercontroller : MonoBehaviour {
    public float maxSpeed = 10f;
    public float jumpForce = 700f;
    bool facingRight = true;
    bool grounded = false;
    public Transform groundCheck;
    public float groundRadius = 0.2f;
    public LayerMask whatIsGround;
    
    public float move;
    
    // Use this for initialization
    void Start () {
        
    }
    
    // Update is called once per frame
    void FixedUpdate () {
        
        
        grounded = Physics2D.OverlapCircle (groundCheck.position, groundRadius, whatIsGround);
        
        move = Input.GetAxis ("Horizontal");
        
    }
    
    void Update(){
        if (grounded && (Input.GetKeyDown (KeyCode.W)||Input.GetKeyDown (KeyCode.UpArrow))) {
            
            rigidbody2D.AddForce (new Vector2(0f,jumpForce));
        }
        rigidbody2D.velocity = new Vector2 (move * maxSpeed, rigidbody2D.velocity.y);
        
        if (move > 0 && !facingRight)
            Flip ();
        else if (move < 0 && facingRight)
            Flip ();
        
        
        
        if (Input.GetKey(KeyCode.Escape))
        {
            Application.Quit();
        }
        
        if (Input.GetKey(KeyCode.R))
        {
            Application.LoadLevel(Application.loadedLevel);
        }
        
        
    }
    
    void Flip(){
        facingRight = !facingRight;
        Vector3 theScale = transform.localScale;
        theScale.x *= -1;
        transform.localScale = theScale;
    }       
}

groundCheck = transform.Find("plaforma");
//или так
groundCheck = gameObject.Find("plaforma");

groundCheck = gameObject.Find("plaforma").transform;