While avoiding a scientific/chemical definition of what fun is, what fun is to me is the raw application of my brain, feelings of in the moment pure experience, and physical reward in different combinations. Games that are fun to me are ones that can distract me from the real world, without boring me, and possibly while providing reward. This is why I like looking though my microscope. You are forced to bring your attention and focus to a pinpoint, which can distract you from all the terrible of the world, and allows you to set up small goals, succeed and then get rewards. I want to focus my eyes, because I want the mental reward of being a scientifically involved individual and of knowing what the microscopic world looks like, and in the moment of looking only at a microscopic cross section of onion I can discover tangible feelings of success and satisfaction that are worth coming back to. I get similar feelings when reading, or getting lost in the plot of a film, and those give me similar rewards of feeling more cultured or more informed than I was before starting. Spending time at my job, deeply entrenched in studying, and physical labor provide the exact same feelings. Chopping wood provides in the moment feelings of distraction, feelings of pure focus and zen, feelings of reward( adrenaline/epinephrine plus the fact that I now have burnable wood) , which are all feelings I associate with fun. So yes, I would agree with the assertion made by Mark Twain, that work and play are indeed the same energy/power/thing in different contexts. ( *note, the feelings and mental processes involved in “finding the zen” of an activity is hard to explain, and I would claim it is even undoable with human language. These ideas and feelings are very abstract, and I didn’t put enough in to really describe them to a reader, so I apologize).