You are phenomenally talented.
You have created an exceptionally thoughtfully programmed game. This should be a standard for other flash games.
1) Your exposition for the player is extremely smart. You do not need a tutorial because the game incorporates the tutorial into the storyline and description. The "forgot the keep out" sign is brilliant from a developer side. You are flagging the notion of "hidden areas" for the player in a way that is subtle and cohesive with the plot.
I also wasn't sure if the "one sec..." when speaking to William was saving the game. However if it was, another smart and subtle addition.
2) Visually, as others have noted, this is stunning. The multi-layered backgrounds are great and detailed. The color and contrast changes in the background with the Ohnem (sp?) denote the eerie mood perfectly.
3) The controls are delightful. The fox feels very "floaty" and it's perfect. Sometimes I felt it was perhaps a hair *too* floaty but it was not distracting.
4) The additional powerups were a marvelous addition. The "sight" one was excellent - when I saw the scope of the map and initially thought I might potentially spend an hour searching for the last items I anticipated knocking this game a couple points. However, once again you anticipated this before it happened and addressed it in the game.
I would absolutely love to see you create a game like this with an expanded universe, different areas, and more puzzles. I would probably pay money for it.