Drag: rotate the camera. Wheel or pinch: zoom. W A S D / arrows: move, Q E: turn. Click a building to inspect it; open Build (castle button) to place buildings, R rotates, Esc cancels. Space pauses. Minimap click flies there.
The science
Population. Growth is logistic, dP/dt = r g P (1 − P/K) + m (1 − P/K), with K the housing capacity (6 per house, 24 in the town hall), r = 0.012 per hour, g a happiness/sanitation factor and m = 0.25 settlers per hour; over capacity people leave, with no food the town shrinks. The closed form is P(t) = K / (1 + ((K − P0)/P0) e−rt).
Harvest. Farm output follows the year: f(d) = 0.8 + 0.35 cos(2π(d − 200)/360), peaking mid-July and lowest in January; spring is below average, which is why the food surplus is modest at the start. Unmilled grain loses 20 % to spoilage; windmills mill it.
Wind. A windmill converts P = ½ ρ A v3 Cp with ρ = 1.225 kg/m³, blade radius 9 m, Cp = 0.30 (a real sail mill is below the Betz limit 16/27 = 0.593). Milling capacity is scaled to the power at the 6 m/s design wind.
Food and heat. Each citizen eats 0.125 units/h (1 unit ≈ 100 kg grain), guards a little more; in cold months households burn wood, 0.05 × population × cold(d).
Labour. Workers are 62 % of the population minus guards; every production building has job slots, and output scales with staffing = min(1, workers/jobs). Lumber output also scales with trees nearby (forest factor), stone needs a rock outcrop.
Money. Gold = tax (per citizen, scaled by the tax slider and a happiness efficiency) + market trade − upkeep. Market prices follow stock with elasticity 0.5: price = base (ref/stock)0.5. Happiness is a sum of simple terms (food, market, church, wells, walls, guards, taxes, research) smoothed over time.
Old quarter and harbour. The realm starts as a hamlet of 48 people with housing for 60 (six lived-in houses plus the town hall, 6 x 6 + 24). The many other houses are empty: restoring one costs 30 gold and 30 timber and adds 6 housing, which is what lets the logistic curve climb. A merchant ship is moored for 2 days in every 6 once a market stands; selling goods then pays +30 %. These are illustrative game rules, not medieval records.
Honest limits. All gold prices, costs, yields and the raid model are illustrative game constants, not medieval statistics; real towns of 1250 had very different economies. The raid event compares a defence rating with a rising threat; no fighting is shown. Buildings, towers, ships, stalls, the pier and the knight were modelled in Blender; population, economy and seasons run in the page.