I would enjoy it much more if there wasn't the whole certain days left aspect. It get's annoying and will cause most to lose interest just like me... plus it waste's important gaming time of my life.
The code your searching for @math master should be written on the phone box near the doorway into the room where you find the door handle. The room before the stairs. The box is hanging on the wall.
I think the simple cliff hanger has done it's job... You all are now either moaning or requesting a sequel.So the developer has you wrapped around his little finger, only time will tell if he makes a sequel or not. I myself personally hope he does.