The plugin displays the current situation and offers a button to advance to the next year. Each year is recorded in the Journal so that one can return to play years over.
In year 1 the population is now 100.
You have 2800 bushels in storage.
The city owns 1000 acres of land.
The ruler's decisions are recorded in markup and can be revised at any time.
Say BUY or SELL acres — at market rates.
Say FEED bushels — to people, 20 bushels each.
Say PLANT acres — one bushel seed per acre.
See Hammurabi Project that intends to capture a half-dozen individually meaningful "snippets" of code that can be assembled in principle to build this plugin.