Not really, or it shouldn't be. If you have a few hours to spare each day on this hobby and you sit down each day and make a video game that you want to make, in very short time you might have five or ten different games that you've come up with, especially if you're impatient or have a number of different ideas.
You have to consider that a prototype can be very, very rough. If it takes 12 months to make a prototype of a video game, then that's the wrong way to go about making a prototype. This is assuming that the core premise of the game doesn't involve inventing something impossible or solving the halting problem. Even if it involved something tough, you would just have to "fake it" until you figure out what you want to make, anyway.
You should also pick a platform that lets you do things easily, and limit the time you spend. If what motivates you about a game idea is the art and you spend most of your time designing characters or worlds, then after a while you have to treat that as your prototype or put in the minimal effort to combine them, instead of making cut-scenes and making a Final Fantasy game from everything.
The audience for the prototype isn't the final audience either. Maybe it can be friends if they're uncritical but you should really just make it for yourself if you're still in the picking an idea phase.
You have to consider that a prototype can be very, very rough. If it takes 12 months to make a prototype of a video game, then that's the wrong way to go about making a prototype. This is assuming that the core premise of the game doesn't involve inventing something impossible or solving the halting problem. Even if it involved something tough, you would just have to "fake it" until you figure out what you want to make, anyway.
You should also pick a platform that lets you do things easily, and limit the time you spend. If what motivates you about a game idea is the art and you spend most of your time designing characters or worlds, then after a while you have to treat that as your prototype or put in the minimal effort to combine them, instead of making cut-scenes and making a Final Fantasy game from everything.
The audience for the prototype isn't the final audience either. Maybe it can be friends if they're uncritical but you should really just make it for yourself if you're still in the picking an idea phase.