I hadn't posted my example yesterday because this second example is where I ran into a problem. At the time, I wanted to try fixing it first, but then after lunch, I just forgot...

But I don't think I'll bother now. Moho's particle emitter apparently always emits randomly in 3D space, even when there is no actual depth--in other words affecting 2D stacking order, and there is no way to fix the stacking order. (Maybe in a future version?)
I'll post the two project files shortly.

