When I first became seriously interested in game design a little less than a decade ago, I often struggled with the question of whether a concept was a “valid game.” I wasn’t trying to figure out whether the concept was good–I knew that most ideas wouldn’t pan out–but whether it had the potential for fun play. Now, all these years later, trying to figure out why the prototype in the previous post wasn’t as much fun as I had expected gave me the way to analyze that question. To decide whether your concept can produce a valid game, you need to determine what kind of decision the player will make and why that decision will be interesting.

By what kind of decision I mean more than just “the player will try to shoot the bad guys.” Will the player test her dexterity by aiming with a mouse? Maneuver his limited resources on a map? Select a number of chips to bet against a roll of the dice? Strip the game’s theme away, and ask what the player will physically do during the game.

When deciding why that decision will be interesting, think through how that decision (again, the physical thing the player does, not the conceptual activity represented thereby) will work in practice. Is the player going to have multiple possibilities to choose from? What will prevent the player from detecting and picking the right answer every time? After the decision’s consequences have played out, will the player feel like the choice mattered? How long will it take for those consequences to emerge? Is that fast enough for the player to recognize the consequences as feedback, or will they just seem random?

My last prototype failed because I didn’t finish the second question. It looked like there were going to be lots of options, but in practice there was only ever one or two–and only one of them was ever reasonable. Had I really thought the problem through, I would have recognized that I was going down a dead end.

What kind of decision will the player make? Why will that decision be interesting? If you can answer both of those satisfactorily, you have something at least worth considering.