Gyroscope default position

I have a question about gyroscope delault position. I created a game in witch you move space ship foward, back, left, and right by moving the phone(using gyroscope). My problem is that I must hold phone like on picture 1. If i hold the phone like on picture 2, the ship goes down. Anyone know how to change default position of the gyroscope, so I can normally hold the phone and steering the ship? I want the ship stationary if my phone is holded at 45 degrees. Otherwise, it move to the titled direction.

My code:

using UnityEngine; using System.Collections;

[System.Serializable] public class Boundaryy { public float xMin, xMax, zMin, zMax; }

public class PlayerControll1 : MonoBehaviour { public float speed; public float tilt; public Boundaryy boundary;

 // Use this for initialization
 void Start () {
     Input.gyro.enabled = true;
     Screen.sleepTimeout = SleepTimeout.NeverSleep;
 }
 
 
 
 
 void FixedUpdate() {
     float xi = Input.gyro.userAcceleration.x;
     float yi = Input.gyro.userAcceleration.y;
     
     Vector3 movement = new Vector3 (xi, 0.0f, yi);
     rigidbody.velocity = movement * speed;
     
     rigidbody.position = new Vector3 
         (
             Mathf.Clamp (rigidbody.position.x, boundary.xMin, boundary.xMax), 
             0.0f, 
             Mathf.Clamp (rigidbody.position.z, boundary.zMin, boundary.zMax)
             );
     
     rigidbody.rotation = Quaternion.Euler (0.0f, 0.0f, rigidbody.velocity.x * -tilt);
     
     
 }
 
 
 

}