//Platform - платформа на которой стоит игрок
    //rigibody - переменная равна GetComponent<Rigidbody>();    
    //Gravity - моя переменная.
    float curDir = 0f; // compass indicating direction
    void FixedUpdate()
    {
        float turn = Input.GetAxis("Horizontal");
        curDir = (curDir + turn) % 360;
        RaycastHit hit;
        Physics.Raycast(new Ray(transform.position, -transform.up),out hit);                
        var rot = Quaternion.FromToRotation(Vector3.up, hit.normal);
        var oldrot = rigibody.rotation;
        rigibody.rotation = rot*Quaternion.Euler(0, curDir, 0);        
        rigibody.AddForce(-Platform.up * Gravity);
        rigibody.AddForce(transform.forward * Input.GetAxis("Vertical") * 10 * Speed);
    }

var rot = Quaternion.FromToRotation(Vector3.up, hit.normal);     
rigibody.rotation = rot;