Thanks so much for your message. Really glad you enjoyed our game! :)
The way ressources work at the moment, is that you get +1 at start of the game, and once you put your first building it goes as follows :
food = floor(number of windmills * number of vacant fields/2) + 3
Same for food.
Population drops drastically if their is no food for two ticks in a row. And population grows if their is excess food for two ticks (it then consumes 2 food for each birth).