SimpleParticleShooting.cs

/* Weapon.cs */
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Weapon : MonoBehaviour
{
    [SerializeField]
    private new ParticleSystem particleSystem;

    [SerializeField]
    private float damage;

    [SerializeField]
    private float fireRate;

    private List<ParticleCollisionEvent> collisionEvents;

    private string enemyTag;

    private bool fireCooldown;

    void Start()
    {
        collisionEvents = new List<ParticleCollisionEvent>();
    }

    void OnParticleCollision(GameObject other)
    {
        ParticlePhysicsExtensions.GetCollisionEvents(particleSystem, other, collisionEvents);

        for (int i = 0; i < collisionEvents.Count; i++)
        {
            var collider = collisionEvents[i].colliderComponent;
            if (collider.CompareTag(enemyTag))
            {
                var health = collider.GetComponent<HealthController>();
                health.ApplyDamage(damage);
            }
        }
    }

    public void Fire()
    {
        if (fireCooldown) return;
        fireCooldown = true;
        particleSystem.Emit(1);
        StartCoroutine(StopCooldownAfterTime());
    }

    private IEnumerator StopCooldownAfterTime()
    {
        yield return new WaitForSeconds(fireRate);
        fireCooldown = false;
    }

    public void SetEnemyTag(string enemyTag)
    {
        this.enemyTag = enemyTag;
    }
}

/* WeaponController.cs */
using UnityEngine;

public class WeaponController : MonoBehaviour
{
    [SerializeField]
    private Weapon weapon;

    [SerializeField]
    private string enemyTag;

    private bool fire;

    void Start()
    {
        weapon.SetEnemyTag(enemyTag);
    }

    void Update()
    {
        if (Input.GetMouseButtonDown(0))
        {
            fire = true;
        }

        if (Input.GetMouseButtonUp(0))
        {
            fire = false;
        }

        if (fire)
        {
            weapon.Fire();
        }
    }
}

/* HealthController.cs */
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class HealthController : MonoBehaviour
{
    [SerializeField]
    private float maxHealth;

    private float currentHealth;

    [SerializeField]
    private float respawnTime;

    [SerializeField]
    private GameObject healthPanel;

    [SerializeField]
    private Text healthText;

    [SerializeField]
    private RectTransform healthBar;

    private float healthBarStartWidth;

    private MeshRenderer meshRenderer;
    
    private bool isDead;

    void Start()
    {
        meshRenderer = GetComponent<MeshRenderer>();
        currentHealth = maxHealth;
        healthBarStartWidth = healthBar.sizeDelta.x;
        UpdateUI();
    }

    public void ApplyDamage(float damage)
    {
        if (isDead) return;

        currentHealth -= damage;

        if (currentHealth <= 0)
        {
            currentHealth = 0;
            isDead = true;
            meshRenderer.enabled = false;
            healthPanel.SetActive(false);

            StartCoroutine(RespawnAfterTime());
        }

        UpdateUI();
    }

    private IEnumerator RespawnAfterTime()
    {
        yield return new WaitForSeconds(respawnTime);
        ResetHealth();
    }

    private void ResetHealth()
    {
        currentHealth = maxHealth;
        isDead = false;
        meshRenderer.enabled = true;
        healthPanel.SetActive(true);
        UpdateUI();
    }

    private void UpdateUI()
    {
        float percentOutOf = (currentHealth / maxHealth) * 100;
        float newWidth = (percentOutOf / 100) * healthBarStartWidth;

        healthBar.sizeDelta = new Vector2(newWidth, healthBar.sizeDelta.y);
        healthText.text = currentHealth + "/" + maxHealth;
    }
}

/* Movement.cs */
using UnityEngine;

public class Movement : MonoBehaviour
{
    private Rigidbody rigidbody;

    [SerializeField]
    private float speed;

    [SerializeField]
    private ForceMode forceMode;

    // Start is called before the first frame update
    void Start()
    {
        rigidbody = GetComponent<Rigidbody>();
    }

    // Update is called once per frame
    void Update()
    {
        float h = Input.GetAxis("Horizontal");
        float v = Input.GetAxis("Vertical");
        Vector3 velocity = new Vector3(0, 0, v);
        velocity *= speed;
        velocity -= rigidbody.velocity;

        rigidbody.AddForce(velocity, forceMode);
    }
}