I have a friend who is a mathematician but a puzzler at the same time.
Whenever I call him and ask him what he is doing, he gives an awkward answer,
Like when he was working on vectors , he told me "I am figuring out directions to my way home."
when he was working on 3-D,he said "I am sorting my workspace."
Yesterday when I called him, he said "I am fixing ceiling and roof of my house."
What is he working on?