*Warning spoiler* please play the game before you read this, you'll enjoy it
I just finished the game as well but after the ending I just wanted to keep going, to keep finding answers. This game dictates the mood of the user throughout the whole game and I felt that is where the key to the whole story of the game lies, its us who make up the story behind the game and to make our own conclusions.
To me the story of the game was that the boy was in search of some sort of answer, at the start of the game you get no picture of whats going on, but at the end you get a taste of what he was searching for. My conclusion from the ending was that he died from some accident and he was in search for whether his sister had survived or also suffered the same fate. At the beginning you are filled with confusion with the simple forest setting, and the multiple layered background and of course everything is in black and white, plus that eery white noise just adds to that conclusion. Nonetheless the game is based on the boy going through a journey of obstacles which heavily revolve around one outcome "death". Through the game the setting changes from a simple and natural forest environment into a mechanical and almost unrealistic type setting with clockwork machinery and anti gravity machines. These to me show that the boy goes from a confused state of mind regarding the reality of his sister's fate, he then tries to create some sort of logical yet imaginary world filled with objects and mechanisms that make him feel in some sort of false sense of security because he doesn't want to learn the real fate of his sister. Up until the end where he flies through that pane of glass he enters back into the forest or maybe he enters back into reality, the scenery is almost the same as at the beginning but there is one difference, instead of just white noise you get this nice harmonic sound that kind of removes that confused feeling, then as he walks further into the woods, he faces what he was seeking for, the sound then goes back to white noise, but this time we don't feel confused but we feel speechless as if the boy found the answer he was seeking for but the answer was not what he wanted to believe.