“This isn’t an algorithm for fun, but it’s a useful tool for checking for the absence of fun, because designers can identify systems that fail to meet all the criteria. It may also prove useful in terms of game critique. Simply check each system against this list: Do you have to prepare before taking on the challenge? Can you prepare in different ways and still succeed? Does the environment in which the challenge takes place affect the challenge? Are there solid rules defined for the challenge you undertake? Can the core mechanic support multiple types of challenges? Can the player bring multiple abilities to bear on the challenge? At high levels of difficulty, does the player have to bring multiple abilities to bear on the challenge? Is there skill involved in using an ability? (If not, is this a fundamental “move” in the game, like moving one checker piece?) Are there multiple success states to overcoming the challenge? (In other words, success should not have a single guaranteed result.) Do advanced players get no benefit from tackling easy challenges? Does failing at the challenge at the very least make you have to try again? If your answer to any of the above questions is “no,” then the game system is probably worth readdressing.”