The whole map is in the form of a series of self-contained "biomes" or levels, with unique configurations.
Every level has the types of resources required to solve the puzzle, but not necessarily all types of resources. For example, different types of metal can be found in different biomes.
The train moves through the biomes in a single direction
As the Fog blows through, the biomes begin to die - if left long enough without disturbance, they can regenerate a percentage of their original health, but eventually stop recovering altogether. This signifies the final pass before the game ends.