I'm really enjoying this game. Congratulations, it feels nice to interact with. I was a bit confused about how to use/access tier two buildings though. I tried clicking the icon / using some different key commands to select the II icon.
Otherwise thanks again for making it :)
EDIT: I worked it out. I think the first time the tiers unlocked the game also prompted me to change to a new map so I missed the part where I was developing things further after stage 1. A bit of a game flow thing