Sometimes when i think about a game idea, i always check that every brick , every gameplay rule makes sense in some way. For example, look at the Flash game Earn To Die http://thegamerstop.com/45717-Earn-to-Die-2012.html When you kill zombies, you earn $$ out of nothing, which is nonsense. Ok it is a fun game overall, but i think it would be even better if the game explains at least why i am earning $$ for killing zombies.. i don't know... maybe zombies have cash in their pocket because they were honest human workers before turning into zombies and they had a job, and so after killing them i can rob them. It's the first stupid thing that came up to my mind just now that i am writing this line.. but at least it's a motivation In the game that is not evident, it is like the money prize is something forced. So, is it a good rule of thumb to ask themselves if every single thing makes sense? Otherwise it is not fun or not as fun as it could be ? I'm not sure.. sometimes i think about Mario 64 when you win coins after you beat a Goomba.... why is that?? But anyway M64 had success. P.S. How is it called the game genre of Earn To Die and similar ones? Maybe "iterative survival game"? I said iterative because after you die you always restart again from the beginning.