[sokoloff]

Wouldn’t a doubling of all squares (and replacement of one of those with a block where walls existed) do it? (It’s not clear that you could totally reliably do that in your head while doing whatever other editing/creation task was needed, but the naive algorithm seems pretty straightforward.)

[colordrops]

Yes, you've got it exactly correct - I was able to draw it out using a simple algorithm, but couldn't do it mentally in-game by looking at the original.