Máu, sát thương và cảm giác trúng đòn

using System;
using UnityEngine;

//bên trong CharacterStats

//máu hiện tại và máu tối đa
public event Action<float, float> OnHealthChanged;
public event Action OnDied;

public void TakeDamage(float rawDamage)
{
    if (!IsAlive) return;

    float reduced = Mathf.Max(1f, rawDamage - finalDefense);
    currentHealth = Mathf.Max(0f, currentHealth - reduced);

    OnHealthChanged?.Invoke(currentHealth, finalMaxHp);   // báo cho ai đang nghe
    DamagePopup.Spawn(transform.position + Vector3.up * 2f, reduced);

    if (!IsAlive)
    {
        OnDied?.Invoke();
        Die();
    }
}

public void Heal(float amount)
{
    if (!IsAlive) return;
    currentHealth = Mathf.Min(finalMaxHp, currentHealth + amount);
    OnHealthChanged?.Invoke(currentHealth, finalMaxHp);
}

using UnityEngine;
using UnityEngine.UI;

public class HealthBar : MonoBehaviour
{
    [SerializeField] private CharacterStats stats;
    [SerializeField] private Image fill;
    [SerializeField] private Image trailing;      // thanh vàng chạy sau
    [SerializeField] private float trailSpeed = 1.2f;

    private Camera cam;
    private float target = 1f;

    void Awake() => cam = Camera.main;

    void OnEnable()
    {
        stats.OnHealthChanged += Redraw;
        stats.OnDied += () => gameObject.SetActive(false);
    }

    void OnDisable() => stats.OnHealthChanged -= Redraw;   // luôn nhớ huỷ đăng ký

    void Redraw(float current, float max)
    {
        target = max <= 0f ? 0f : current / max;
        fill.fillAmount = target;                          // tụt ngay
    }

    void LateUpdate()
    {
        // thanh chạy sau tụt từ từ — chính nó làm người chơi thấy rõ mất bao nhiêu máu
        trailing.fillAmount = Mathf.MoveTowards(trailing.fillAmount, target, trailSpeed * Time.deltaTime);

        //luôn quay mặt về camera
        transform.rotation = cam.transform.rotation;
    }
}

using UnityEngine;
using TMPro;

public class DamagePopup : MonoBehaviour
{
    private static DamagePopup prefab;

    [SerializeField] private TextMeshProUGUI label;
    [SerializeField] private float lifeTime = 0.8f;
    [SerializeField] private float riseSpeed = 1.6f;

    private float age;

    public static void Spawn(Vector3 worldPos, float amount)
    {
        if (prefab == null)
            prefab = Resources.Load<DamagePopup>("DamagePopup");   // Assets/Resources/DamagePopup.prefab
        if (prefab == null) return;

        DamagePopup p = Instantiate(prefab, worldPos, Quaternion.identity);
        p.label.text = Mathf.RoundToInt(amount).ToString();

        //lệch nhẹ để hai cú đánh không chồng nhau
        p.transform.position += new Vector3(Random.Range(-0.3f, 0.3f), 0f, 0f);
    }

    void Update()
    {
        age += Time.deltaTime;

        transform.position += Vector3.up * riseSpeed * Time.deltaTime;
        transform.rotation = Camera.main.transform.rotation;

        float t = age / lifeTime;
        label.alpha = 1f - t;                                     // mờ dần
        transform.localScale = Vector3.one * (1f + 0.3f * (1f - t));

        if (age >= lifeTime) Destroy(gameObject);
    }
}

using System.Collections;
using UnityEngine;

public class HitFlash : MonoBehaviour
{
    [SerializeField] private CharacterStats stats;
    [SerializeField] private Renderer[] renderers;
    [SerializeField] private float duration = 0.09f;

    private Color[] original;

    void Awake()
    {
        original = new Color[renderers.Length];
        for (int i = 0; i < renderers.Length; i++)
            original[i] = renderers[i].material.color;
    }

    void OnEnable()  => stats.OnHealthChanged += (_, __) => { StopAllCoroutines(); StartCoroutine(Flash()); };

    IEnumerator Flash()
    {
        foreach (Renderer r in renderers) r.material.color = Color.white;
        yield return new WaitForSeconds(duration);
        for (int i = 0; i < renderers.Length; i++) renderers[i].material.color = original[i];
    }
}