Unity 里在Script不能运行，报错为error0246：The type of nameplace "#" could not be found

在unity里assets下创建script文件夹，写好了两个程序文件分别为Player和PlayerController，但是点击开始不能正常运行

问题相关代码
Player:

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

[RequireComponent (typeof (PlayerController))]
public class player : MonoBehaviour{

    public float moveSpeed = 5;
    PlayerController controller;

    void Start() {
        controller = GetComponent<PlayerController> ();
    }

    void Update(){
        Vector3 moveInput = new Vector3 (Input.GetAxis ("Horizontal"),0,Input.GetAxis ("Vertical"));
        Vector3 moveVelocity = moveInput.normalized * moveSpeed;
        controller.Move(moveVelocity);
    }
}

PlayerController:

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

[RequireComponent (typeof (Rigidbody))]
public class playercontroller : MonoBehaviour {

    Vector3 velocity;
    Rigidbody myRigidbody;

    void Start(){
        myRigidbody = GetComponent<Rigidbody> ();
    }

    public void Move(Vector3 _velocity){
        velocity = _velocity;
    }

    public void FixedUpdate(){
        myRigidbody.MovePosition (myRigidbody.position + velocity * Time.fixedDeltaTime);

    }

}

运行结果及报错内容

怎么解决这个问题？求解答__

大小写