The interface is simple: everything takes place in the bottom pane, where you'll find four tabs: Info, Material, Workers, Building. The Info tab shows you the basic stats of the kingdom, such as population, number of citizens the town can support, the amount of food provided, etc. Additionally, you'll find here the objectives of the level, which usually feature multiple items: "make x amount of money", "build a particular kind of building", grow kingdom to a certain size", etc.

The Material tab is where you'll purchase the building materials that go into the creation of all buildings. These are simple enough: wood and stone. Your citizens never mine these resources; they're always bought, and there are different prices depending upon how much of each you want to buy. There might be more materials in the full version of the game; I'm writing this based on the demo.

The Workers tab is where you'll purchase workers to build your structures, and a hero to defend your town. More on this later.

Finally, the Building tab is where you'll spend most of your time. Be a King starts you off in the early days of the kingdom, with access to just a few buildings. These include dwellings, food production, service, and military. The dwellings are houses, which are arguably the key buildings in the game, as each house provides inhabitants which pay taxes, increasing the wealth of the kingdom. As stated, each building has three levels to build, and each level increases the value of the structure. Thus, a Level One house will hold a certain number of inhabitants, and these generate income. Level Two inhabitants generate even more income, etc., up to Level Three. Interestingly, upgrading a building costs less than the initial purchase, which is a factor to consider when deciding whether or not to purchase a new building to add to the overall pool, or just to upgrade existing structures.

One of the deciding factors in constructing a new building is the number of available workers. Unlike most kingdom building games, these workers aren't pulled in from the existing populace; they can be purchased in the Workers tab of the interface. Once purchased, these workers are always part of the workforce. Another factor is the amount of gold needed, and a third is the amount and type of material needed. Hovering your cursor over a building type will show what you'll need to create that building.

Other important buildings are the food production and military types. The food production type is a farm, which generates food to feed the kingdom's inhabitants. This building can also be upgraded to yield more food. Without enough food, the population of the kingdom will slowly decrease. The military building is a barracks, which accomplishes a couple of things: 1) It adds to the overall security of the kingdom, and 2) It defends the kingdom by automatically attacking monsters that wander in from nowhere.