创建一个2d正方形（9-Sliced）命名为Player，在Player下面新建一个画布（Canvas）命名为PlayerHealthUI，在画布下面新建一个滑动条（Slider）命名为HealthBar

把PlayerHealthUI脚本挂载到PlayerHealthUI上，拖拽情况如图所示

using UnityEngine;
using UnityEngine.UI;

public class PlayerHealthUI : MonoBehaviour
{
    [SerializeField] private Slider healthBar;
    [SerializeField] private Health health;

    //更新血条方法（注意要写成公有的）
    public void UpdateUI()
    {
        healthBar.value = health.Value;
    }

    //进入游戏的时候开启
    private void Awake()
    {
        //起始值：血条UI的起始值=health的初始值
        healthBar.maxValue = health.Value;
        //更新：血条UI的现在值=health的初始值
        healthBar.value = health.Value;
    }
}

把playerMovement脚本，Health脚本，Damageable脚本，挂载到Player对象上，拖拽情况如图所示

using UnityEngine;
using UnityEngine.InputSystem;
using DG.Tweening;

public class playerMovement : MonoBehaviour
{

    [SerializeField]private Rigidbody2D rb;
    private Vector2 _inputDirection;
    [SerializeField]private float _speed;
    public void Move(InputAction.CallbackContext context)
    {
        _inputDirection = context.ReadValue<Vector2>();
       
    }

    private void FixedUpdate()
    {
        var position = (Vector2)transform.position;
        var targetPosition = position + _inputDirection;
        if (position == targetPosition) return;
        rb.DOMove(targetPosition, _speed).SetSpeedBased();
    }
}

using UnityEngine;
using UnityEngine.Events;

public class Health : MonoBehaviour
{
    [SerializeField] private int health;
    [SerializeField] private UnityEvent<int> healthchange;
    public int Value
    {
        get { return health; }
    }
    //减少血量
    public void DreaseHealth(int amount)
    {
        //血量减去被传进来的值
        health -= amount;
        healthchange.Invoke(health);
    }

}

using DG.Tweening;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Damageable : MonoBehaviour
{
    [SerializeField]private Health health;
    //想要实现被伤害时变红闪烁一下
    [SerializeField]private SpriteRenderer spriteRenderer;
    public void TakeDamage(int damage)
    {
        health.DreaseHealth(damage);
        //在DG.Tweening包中，记得引入
        //DOColor()需要的两个arguement：第一个是确定颜色，第二个是完成变换所需要的时间
        //再变回去需要SetLoops(),两个arguemengt，一个是变换几圈，一个是以什么方式变
        //红色到白色是一圈，红色到白色是另一圈
        //Yoyo：慢慢变换
        //还需要用ChangeStartValue()给一个起始颜色
        spriteRenderer.DOColor(Color.red,0.2f)
            .SetLoops(2,LoopType.Yoyo)
            .ChangeStartValue(Color.white);

        
    }
}

把Attack脚本和EnemyMovement脚本，挂载到Enemy对象上

using DG.Tweening;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class EnemyMovement : MonoBehaviour
{
    [SerializeField] private Rigidbody2D rb;
    [SerializeField] private float _speed;
    [SerializeField]private PlayerManager playerManager;

    private void FixedUpdate()
    {

        //玩家当前位置
        var playPosition = playerManager.position;
        //敌人自己当前位置坐标
        var position=(Vector2)transform.position;
        //当前距离距玩家位置（移动的方向）
        var direction=playPosition-position; 
        //数字规范（方便计算）
        direction.Normalize();
        //目的坐标
        var targetPosition = position + direction;
        //向目的地移动
        rb.DOMove(targetPosition, _speed).SetSpeedBased();
    }

}

using UnityEngine;
using Timers;

public class Attack : MonoBehaviour
{
    private bool _canAttack = true;
    private void OnTriggerEnter2D(Collider2D col)
    {
        DealDamage(col);
    }

    private void OnTriggerStay2D(Collider2D other)
    {
        DealDamage(other);
    }
    private void CanAttack()
    {
        _canAttack=true;
    }

    private void DealDamage(Collider2D other)
    {
        if (!_canAttack) return;
        //Player为标签
        if (other.CompareTag("Player"))
        {
            var damageable = other.GetComponent<Damageable>();
            damageable.TakeDamage(10);
            //三个argument
            TimersManager.SetTimer(this, 1, CanAttack);
            _canAttack = false;
        }
    }
}

PlayerManager脚本挂载到空物体Manager上面

using UnityEngine;

//获取玩家位置
public class PlayerManager:MonoBehaviour
{
    [SerializeField] private Transform playerTransform;
    
    //任何脚本呼叫PlayerManager时，都可以获得玩家位置
    public Vector2 position
    {
        get { return playerTransform.position; }
    }
}