using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.SceneManagement;

public class PlayerHP : MonoBehaviour {

	public int HP = 30;
	public Slider hpSlider;
	public AudioClip soundA;
	public AudioClip soundB;

	void Start () {
		hpSlider.value = HP;
	}
	
	void OnCollisionEnter(Collision other){
		if (other.gameObject.tag == "EnemyBullet") {

			Destroy (other.gameObject);

			if (HP > 0) {
				AudioSource.PlayClipAtPoint (soundA, Camera.main.transform.position);

			} else {
				AudioSource.PlayClipAtPoint (soundB, Camera.main.transform.position);
				Invoke ("Retry", 1.0f);
				return;
			}

			HP -= 1;
			hpSlider.value = HP;
		}
	}

	void Retry(){
		SceneManager.LoadScene ("Main");
	}

	// ★追加
	public void AddHP(int amount){
		HP += amount;

		if (HP > 30) {
			HP = 30;
		}

		hpSlider.value = HP;
	}
}
C#

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class HPItem : MonoBehaviour {

	public AudioClip getSound;
	private PlayerHP pHP;

	void Start(){
		pHP = GameObject.Find ("PlayerBody").GetComponent<PlayerHP> ();
	}

	void OnTriggerEnter(Collider other){
		if (other.gameObject.tag == "Player") {
			Destroy (gameObject);
			AudioSource.PlayClipAtPoint (getSound, Camera.main.transform.position);
			pHP.AddHP (5);
		}
	}
}
C#