One of my later math teachers used to joke that there were three difficulty levels for proofs in mathematics: trivial, easy, and comfy. In hindsight I believe h

One of my later math teachers used to joke that there were three difficulty levels for proofs in mathematics: trivial, easy, and comfy. In hindsight I believe he was right: even the toughest proofs require more of you to be comfortable with some relevant concepts than anything else.