（スクリプト）

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.SceneManagement;

public class MonsterHP : MonoBehaviour
{
    private int monsterMaxHP = 15;
    private int monsterHP;
    public GameObject effectPrefab;
    public AudioClip sound;
    public Slider HPSlider;
    public Text HPlabel;

    void Start()
    {
        monsterHP = monsterMaxHP;
        HPSlider.maxValue = monsterMaxHP;
        HPSlider.value = monsterHP;
        HPlabel.text = "" + monsterHP;
    }

    private void OnTriggerEnter(Collider other)
    {
        if (other.CompareTag("Stick"))
        {
            monsterHP -= 5;

            if (monsterHP == 0)
            {
                SceneManager.LoadScene("GameOver");
            }
            HPSlider.value = monsterHP;
            HPlabel.text = "" + monsterHP;
            GameObject effect = Instantiate(effectPrefab, transform.position, Quaternion.identity);
            AudioSource.PlayClipAtPoint(sound, Camera.main.transform.position);
        }
    }

    // 追加（やりダメージ）
    private void OnCollisionEnter(Collision collision)
    {
        if(collision.gameObject.CompareTag("Yari"))
        {
            monsterHP -= 3;

            HPSlider.value = monsterHP;
            HPlabel.text = "" + monsterHP;
            GameObject effect = Instantiate(effectPrefab, transform.position, Quaternion.identity);
            AudioSource.PlayClipAtPoint(sound, Camera.main.transform.position);

            if(monsterHP < 0)
            {
                SceneManager.LoadScene("GameOver");
            }
        }
    }
}