NPC.cs - With Particles!

using System;
using UnityEngine;

public class NPC : MonoBehaviour
{
	[SerializeField]
	private int startingHp = 100;
	[SerializeField]
	private UnityEngine.UI.Slider hpBarSlider;
	[SerializeField]
	private ParticleSystem deathParticlePrefab;

	private int _currentHp;

	private void Start()
	{
		currentHp = startingHp;
	}

	internal void TakeDamage(int amount)
	{
		if (amount <= 0)
			throw new ArgumentOutOfRangeException("Invalid Damage amount specified: " + amount);

		currentHp -= amount;

		UpdateUI();

		if (currentHp <= 0)
			Die();
	}
	
	private void UpdateUI()
	{
		var currentHpPct = (float)currentHp / (float)startingHp;

		hpBarSlider.value = currentHpPct;
	}

	private void Die()
	{
		PlayDeathParticle();
		GameObject.Destroy(this.gameObject);
	}

	private void PlayDeathParticle()
	{
		var deathparticle = Instantiate(deathParticlePrefab, transform.position, transform.rotation);
		Destroy(deathparticle, 4f);
	}
}