If I'm going to create a multiplication effect for a 2D game, where should I start?

As you can see, the projectiles thrown by the Boss explode after hitting the wall. Of course, I won’t do pixelart, it will be a stylized vfx. But it is made with particle, the logic of which I don’t understand, or does it appear to be a spritesheet? I would be happy if you give me advice.