Getting started

A rough design for my next game is finally coming together in my head. Assignment was only to create a shooter type of game so the possibilities were virtually endless. Decided on a dark, gloomy mansion you have to escape from while solving problems. Love me some puzzles. And yes, there will be shooting as required. Enemies may be ghosts, rats or nosy neighbours, haven't decided yet.

I've already begun modelling the house and rooms where the player can roam around and also programmed the player's movements (only a cube at this point). 

I make up the details as I go so will probably drive myself into a corner at some point because of that. Will I learn from it?

Also, the game will NOT be called Marilyn Mansion when it's done.