What subjects did Donato Bramante study in his lost theoretical writings?

Although most of Donato Bramante’s theoretical writings have been lost, their subjects are known and reflect his diverse professional interests. Aside from his report on the tiburio (crossing tower) of the Milan Cathedral, his lost works included writings on the following subjects:

• Perspective: Reflecting his expertise and early career as a painter of illusionistic architectural settings.
• The "German manner": A study focused on Gothic architecture.
• Fortification methods: Practical treatises on military engineering and defense structures.

These subjects highlight the breadth of his intellectual curiosity, which extended beyond his primary work as an architect and painter to include technical and theoretical analysis of building styles and structural design.1