A Dark Room
The player begins in A Dark Room. The only option presented to the player is to light the fire.
A Firelit Room
Once the dark room is lit, the room will become A Firelit Room. The Firelit Room can be upgraded to allow the player the ability to build a variety of structures, craft weapons or supplies, or buy resources from the Trading Post. The Room will report its temperature and the status of the fire whenever entered. The fire may be dead, smoldering, flickering, burning, or roaring, which will cause the room to be freezing, cold, mild, warm, or hot respectively.
If not stoked for a period of time, the fire will degenerate from roaring to burning, etc., with the room cooling as it goes. If the fire tries to fall below flickering, the Builder will stoke it automatically to keep it lit. As the Builder generates a constant +2 wood per 10 seconds, it is impossible for the fire to go out during a continuous play session.
Unless the fire is dead, the state of the fire and temperature of the room does not appear to have any impact on the rest of the game after the Builder recovers, apart from causing a constant slow consumption of wood.