Louis did not leave a son as heir after his death in 1382. Instead, he named as his heir the young prince Sigismund of Luxemburg, who was 11 years old. The Hungarian nobility did not accept his claim, and the result was an internal war. Sigismund eventually achieved total control of Hungary and established his court in Buda and Visegrad. Both palaces were rebuilt and improved, and were considered the richest of the time in Europe. Inheriting the throne of Bohemia and the Holy Roman Empire, Sigismund continued conducting his politics from Hungary, but he was kept busy fighting the Hussites and the Ottoman Empire, which was becoming a menace to Europe in the beginning of the 15th century.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): How old was Sigismund of Luxemburg when he was named heir?
11