Ошибка в коде (20,29): error CS0723: Cannot declare a variable of static type 'InputSystem'

вот код:
using Unity.Burst;
using Unity.Collections;
using Unity.Jobs;
using UnityEngine;
using UnityEngine.InputSystem;


namespace Player
{
[RequireComponent(typeof(CharacterController))]
public class PlayerMovement : MonoBehaviour
{
[SerializeField] private float _walkSpeed = 5;
[SerializeField] private float _runSpeed = 8;
[SerializeField] private float _rotateSpeed = 15;
[SerializeField] private float _jumpForce = 5;
[SerializeField] private float _gravity = -9.81f;
[SerializeField] private Transform _cameraRotate;

private InputSystem _inputSystem;
private CharacterController _characterController;

private Vector3 _velocity;
private Vector2 _rotation;

private void Start()
{
_inputSystem = new InputSystem();
_inputSystem.Player.Jump.performed += Jump;
_inputSystem.Player.Move.performed += Move;
_inputSystem.Player.Move.canceled += Move;
_inputSystem.Player.Look.performed += Look;
_inputSystem.Player.Sprint.performed += Move;
_inputSystem.Player.Sprint.canceled += Move;
_inputSystem.Player.Enable();

_characterController = GetComponent<CharacterController>();

Cursor.lockState = CursorLockMode.Locked;
}

private void Move(InputAction.CallbackContext callbackContext)
{
Vector2 direction = _inputSystem.Player.Move.ReadValue<Vector2>() * (_inputSystem.Player.Sprint.IsPressed() ? _runSpeed : _walkSpeed);
Vector3 move = Quaternion.Euler(0, _cameraRotate.localEulerAngles.y, 0) * new Vector3(direction.x, 0, direction.y);
_velocity = new Vector3(move.x, _velocity.y, move.z);
}

private void Look(InputAction.CallbackContext callbackContext)
{
Vector2 mouseDelta = callbackContext.ReadValue<Vector2>() * _rotateSpeed * Time.deltaTime;
_rotation.y += mouseDelta.x;
_rotation.x = Mathf.Clamp(_rotation.x - mouseDelta.y, -90, 90);

_cameraRotate.localEulerAngles = _rotation;

Move(callbackContext);
}

private void Update() => _characterController.Move(_velocity * Time.deltaTime);

private void FixedUpdate()
{
if (_characterController.isGrounded && _velocity.y <= 0f) _velocity.y = -0.1f;
else _velocity.y += _gravity * Time.fixedDeltaTime;
}

private void Jump(InputAction.CallbackContext _) { if (_characterController.isGrounded) _velocity.y = _jumpForce; }

private void OnDestroy()
{
_inputSystem.Player.Jump.performed -= Jump;
_inputSystem.Player.Move.performed -= Move;
_inputSystem.Player.Look.performed -= Look;
_inputSystem.Player.Move.canceled -= Move;
_inputSystem.Player.Sprint.performed -= Move;
_inputSystem.Player.Sprint.canceled -= Move;
_inputSystem.Player.Disable();
}
}
}