I am playing around with some ideas for my DF game, and I just want to run them by you and hear your thoughts on it.

First, I am planning a campaign that revolves around this little concept I came up with. I want the players to change the story according to what their PCs experience (or perceive) - the basic idea is that perception becomes reality. What the players think is going on determines the storyline. I have some ideas for very open-ended stories, and I want the players to use aspects to create the story they think is going on (it's not a secret - the players know that they control the story).

This sounds more complicated than it is. Let me give you an example of a story that illustrates this idea. A young man is under suspicion for having murdered his wife and sister. The player characters are connected to the family in some way – by proximity, relationships, history or by being witnesses – and so they are drawn into the world of the presumed killer. They discover that he believes his wife and sister are evil beings trying to kill him. He is found in a cheap, murky hotel room downtown, where the body of his sister is discovered in the bathtub, her injuries so severe that she cannot be saved. The young man escapes and leaves behind his dying sister. But instead of seeing an innocent young women lying in the bathtub bleeding to death, some of the characters see the sister as the killer sees her; her eyes yellow and bloodied, fingernails sharp as knives dripping with blood and a vicious smile on her contorted lips. She tries to lure the characters closer, only to let out an inhuman hissing sound and with her last ounce of strength, she tries to bury her nails deep in the flesh of the closest player character.

What happens next depends on how the PCs react, what they see (and don't see). Maybe the sister is just in shock, the attack pure instinct - the players decide what the most exciting story is. This obviously will create a lot of challenges, that's why I am asking for input.

I am also interested in creating a "city" on a small scale to be used as locations for the stories. Instead of a city, it will be a series of "stages" (like a rooftop or an apartment building or a single room). This is of course done in collaboration with the players before the story begins. So the locations will determine where the story takes place. Any thoughts on how to do this will be appreciated.

I have much more to tell about the game, but I want to see if anyone has any thoughts before I elaborate further.

Thanks!