void OnCollisionEnter2D(Collision2D other)
    {
        // Friendly code
        if (friendlyBullet)
        {
            EnemyController enemy = other.collider.GetComponent <EnemyController>();
            if (enemy != null)
            {
                enemy.Stun(bulletStun);
                enemy.Damage(bulletDamage);
            }
        }
        // Enemy code
        else
        {
            PlayerController player = other.collider.GetComponent <PlayerController>();
            if (player != null)
            {
                HealthBar.instance.changeValue(-bulletDamage);
                PlayerController.instance.PlayHitSound();
            }
        }

        // If it hit the wall
        WallBoom wall = other.collider.GetComponent <WallBoom>();

        if (wall != null)
        {
            wall.PlayBoom();
        }

        // Instantiate explode
        Instantiate(particles, transform.position, transform.rotation);
        Destroy(gameObject);
    }
 void Awake()
 {
     instance = this;
 }