defrain-shooter-unity/Assets/Scripts/Weapons/Grenade.cs

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

public class Grenade : MonoBehaviour
{
    [SerializeField] GameObject explodeParticle;
    [SerializeField] Weapon weapon; 
    private float countdown;

    void Start() {
        countdown = weapon.Timer;
    }

    void Update() {
        // If grenade has been thrown and countdown is over 0 and grenade has not exploded yet
        if (weapon.HasBeenThrown && !weapon.HasExploded) {
            // Decrease timer by 1 second
            countdown -= Time.deltaTime;
            // If countdown get to 0... BOOM!:
            if(countdown <= 0) {
                // Lets grenade explode
                Explode();
            }
        }
    }


    /* - Spawn explosion particles and add force to nearby objects - */
    private void Explode() {
        // Spawns explosion particle
        GameObject spawnedExplosion = Instantiate(explodeParticle, transform.position, transform.rotation);
        // Destroys explosion particle after on second
        Destroy(spawnedExplosion, 1);
        // Gets all collider that are in a sphere around the grenade
        Collider[] colliders = Physics.OverlapSphere(transform.position, weapon.GrenadeRadius);
        // Iterate over all colliders found in radius
        foreach(Collider nearbyObject in colliders) {
            // Get Rigidbody from nearby object and...
            Rigidbody rb = nearbyObject.GetComponent<Rigidbody>();
            // if rigidbody exists...
            if(rb != null) {
                // adds force to nearby objects
                rb.AddExplosionForce(weapon.ExplosionForce, transform.position, weapon.GrenadeRadius);
            }
        }
        weapon.HasExploded = true;
        // Destroys grenade
        Destroy(gameObject);
    }
}