The Zone – it’s... a very complicated system... of traps, let’s call it, and all of them are deadly. I do not know what happens here, when humans are away, but if only people appear here, everything starts moving. Previous traps disappear, the new ones emerge. The safe places become impassable and the way one moment is simple and easy, the other – turns to be insuperably complicated.
This is the Zone. It may even seem that it is capricious, but in every moment it is such as we made it ourselves... with our inner state. I will not hide, it has happened, that people were forced to return empty-handed from the halfway. There were also such who... perished on the very doorstep of the Room. Nevertheless, everything what happens here, depend not on the Zone, but on us!
Stalker , (Сталкер) — Andrei Tarkovsky, 1979