Slitherine

It is not clear to me what is stated in the manual about having access to tier 2 and 3 buildling.

"Once you have three tier I buildings of one of the sub-categories set out in section 000, you might be offered the chance to build a more powerful tier II building of that type."

Apart that "section 000" typo, what defines a "subcategoriy" ? the background color of the structure or the row where they are ?
In other word, for example, are militar and infrastructure buildings two different sub category or ones ? Because I am noticing that I have access to solid wall (tier 2) although I have just 2 militar buildings.

And for the tier 3 building:

"Once you have six buildings of a type then you might be offered the
chance to build tier III buildings."

what is the type here ? the color or the row ?

Also, why the Large Warehouse has yellow background as a commerce building but it is supposed to be an iinfrastructure one ? Is that a bug ?

the sub-categories are row 1 - food or health, row 2 - military or infrastructure

so if you have 3 food (green), you might then be offered a tier II food, if you have 6 health (blue) then the tier III health buildings pop up

agree about solid walls, I think the quirk is you needed the city walls (tier 1) and its an upgrade of that, so where its a pure upgrade you end up with the situation of say 2 tier 1 and 1 tier 2. No real problem as they all count.

Its one reason why in the mid/late game you can dissamble some tier 1s to create slots and try to fill that slot with tier 3

So if the category are the rows and not the color, if I have 2 food and 1 health i should have access to tier 2 food and health, right ?

no, food is one category, health is another.

they share the row as there are 4 possible allocations for your population