I have always wondered if it meant for something to be hard. The difficulty of tasks, jobs, games, basically everything is brought up in conversation all the time. As a kid I'd argue with my friends about who was taking harder classes, or whose teacher was tougher, or who deserved more kudos for playing a video game on a harder mode (we did this often when we chose different pokemon starters). In university the discussion of hardness became much more refined; problems such as 3SAT were pitted against Vertex-Covers, but the only result that we were able to show was that the problems were “equally” hard. While our discussion became more refined our area of focus was significantly smaller and the scope of saying two problems were in the same class of difficulty is not exactly saying that the problems were exactly equally difficult to solve, just that the two problems can be written in the form of the other problem with a polynomial number of instructions (most of the time). How am I supposed to compare whether or not football is harder than rowing? Or whether chess is easier than other games since top players can play close to optimal (as of the current best chess engines) but in other games such as starcraft or polo the most optimal moves are not even known. I guess we could make some sort of metrics or guidelines. Like solved games are obviously easier than unsolved games (but what if the solution to a solved game takes great difficulty to execute properly?), or that multiplayer games are harder than single player games. But then another question arises, are we talking about the hardness of beating a random person in a game or becoming the best at a game? I have no idea of where to even start, but every so often I think of how to classify the difficulty of random things in the real world. What do you think? How would you go about classifying the difficulty of games or tasks?