So a long, long time ago when I was studying engineering in college, we were assigned “homework sets” where we practiced solving the particular sort of problem we were learning about, often with sets of problems where each built on what you worked out in the last. I just finished a self-assigned homework set to understand the physics of what happens at the start of my current novel. It felt good to exercise my brain, but I am pleased that it is done. Now maybe my brain will let me get back to writing.