How do I make objects spawn on grid?

I have multiple objects falling down from the sky at different rates. However, I never want one to overlap or spawn on the other and always want them fall in a moving grid. For example, imagine something like a tic-tac-toe board on a 20 x infinite grid and there are Xs and Os scattered throughout.

I'm using "Create object" to spawn objects and "Bullet gravity" to set speed.

The way I make grids, is to set the position in intervals of 20 (or any number you want), using this:

Sprite;

Set X to : (round(Sprite.X*0.05))*20

Set Y to : (round(Sprite.Y*0.05))*20

Hmm... the objects are now spawning not from the sky but from the last object and also don't randomly spawn along the X axis.

Wait I think I got it:

X: random(100,600)

Y: -250

Darn. too systematic for the last code i put in. I need it to randomly spawn in any of the grid buckets and not just the same distance each time.

X and Y between ranges but within grid

The way I make grids, is to set the position in intervals of 20 (or any number you want), using this:

Sprite;

> Set X to : (round(Sprite.X*0.05))*20

> Set Y to : (round(Sprite.Y*0.05))*20

What about this for Y?

random(round(-100*0.05)*150,round(-600*0.05)*150)

Set X to : round(sprite.X/gidsize)*gridsize

So for a 32 grid: round(sprite.X/32)*32 . YOu can use the same formula for snapping stuff to the Y axis too.

To make them "fall" on grid increments, use a move +Y:gridsize

Any other movements, have only at the gridsize, and it should never need to be set on the grid again.