Di Chuyen 2D Unity

using UnityEngine;
using System.Collections;

public class PlayerScript : MonoBehaviour
{
    ///
    /// 1 - The speed of the ship
    ///
    public Vector2 speed = new Vector2(50, 50);
    // 2 - Store the movement
    private Vector2 movement;
    void Update()
    {
        // 3 - Retrieve axis information
        float inputX = Input.GetAxis("Horizontal");
        float inputY = Input.GetAxis("Vertical");
        // 4 - Movement per direction
        movement = new Vector2(
            speed.x * inputX,
            speed.y * inputY);
    }
    void FixedUpdate()
    {
        // 5 - Move the game object
        rigidbody2D.velocity = movement;
    }
}