Oh, yes, playing with player's consciousness is a great thing. Imagine wandering the house, for example. You enter the room where you've been ten times already, and... something is different.... slightly... lights are shifted, couple of items fell from the shelf to the floor... you start wondering - does this mean something? was someone(thing) here? or it's merely a game bug? or? then you start to question yours memory... and sanity
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Uncertancy can be much more frightening than any monster.

Uncertancy can be much more frightening than any monster.