Fake Particles visiblity

[zaknafean]

Pretty easy one, but probably worth mentioning that fake particles can be visible and distracting pre explosion as shown in this simple low bit pixel game I'm working on.

The yellow there is the bunched up fake particles I assume.

Easy fix is to set visible = false in _ready, and visible = true before _particles_explode(delta), unless I'm missing some further nuance.