Thank you AlceX, I didn't reinvent the wheel, but as I found nothing satisfactory to create this kind of mechanics, I tried to be inventive to set up something dynamic and tilemap based, the result works indeed rather well! :-)
I see that you are also working on similar universes, especially with Dreams and Reality.
kongregate.com/games/AlceX/dreams-and-reality
Nice game, I just played it and I really liked the concept and the atmosphere. Bravo.