RailCraft

RailCraft is a train simulation game which you can make railway environment on different carpets. 
RailCraft has puzzle levels in it you can gain new rails, environments, trains and carpets by playing those levels.
As you play levels in the same time you can learn how to control everything efficiently. You can create your own levels too. You  can change order of those levels and delete them as you like.
If you create a railway in creative mode and if you want to keep it you can save it and you can open it when ever you like. But you have a limit for saving.