How do I Spawn objects on a grid when off-screen

making an infinite tank shooter game where you shoot to break blocks. The blocks are 10x10 pixels and I used the editor grid snap to place them. Now I want to spawn blocks seamlessly off-screen so it looks like the whole layout is filled with them, and so old cleared areas re-spawn smoothly. Any tips or examples of this? Thanks!

You can create objects in a grid using two nested loops. Here is a 100x50 grid with 20px distance between sprites:

For "x" from 0 to 99
For "y" from 0 to 49
.. Create Sprite at (loopindex("x")*20, loopindex("y")*20)

I kinda have a way it works, but they are not spawning properly. preview.construct.net