Building a house is easy enough
https://www.facebook.com/wiktor.kugelevich/posts/405459986208771
Without stairs, the house is single-storey. With them, it is two-storey. So, let us begin, struggle a bit, and end up with a staircase (for now without railings or decorations) and knowledge of the formulas for "step", "safety", and "comfort", as well as what stringers, bowstrings, balusters, risers, and so on are. In general, building a staircase like this is difficult and even strenuous work—it is oak, after all...