I've never even heard of this correspondence to pen and paper games.

^^ this.

If you interested in making game content for Spring and encounter something you don't recognize, you consult with the docs.
The most commonly used syntax in programming languageges for assigning an expression to a variable is res=exp; which is completely against math rules when used in a=a+1; If this confuses you because you're a mathemathician, you look at the docs.
Just because some syntax might be more intuitive to P&P players or musicians or someone else, it doesn't mean it's better than any other syntax.

This is a direct result of:

I've been looking in the Spring source related to the yardmaps and a inverted "c" cell (let's call it "i" as jk suggested) should be very simple to add and wellcome. The bugs I've encountered is in the closeYard() part where all units must leave the entire yardmap and not only "c" cells, so even if a unit is standing on "y" factory won't close. Also, while under construction all yardmap cells seem to be treated as "o" since I can't place an overlaping building until the first one finishes.