Could be extended like that too. I just didn't want to bother with diagonals at this point lol
Oh, also I was looking for tabletop rpg fantasy maps and I found something that MIGHT give you an idea for you grid system on this store page :
https://www.drivethrurpg.com/product/256706/City-Modular-MapTiles-COTBS
Near the middle of the page, there is an animation of a modular arena, on twitter you said something about shrinking arena so that might be interesting!