It opens on a calendar of twenty five locked doors and a note explaining that it is meant to be played a day at a time through December. It is probably not December, so open the options and turn on ignore date, and the first door lets you in. Behind it is one small thing to do with trees and an axe, and nothing else on the entire calendar is available yet.
Every door after that adds a layer that runs on what the layer before it produced, so the workshop needs what the forest cuts, and the thing on the eighth needs what the fourth has been quietly stockpiling. By the middle of the month you are running a supply chain and going back to fix the bottleneck you built on day three. The twenty fifth door is a real ending, which almost nothing in this genre bothers to have.