I have 64 sand for my glass production. I have another 60 sand 60 water for my concrete production. My windmill get to lvl 25 with two lvl 21 sand on othwe side. But if you have built up a huge steel production to get this far in the game, you will find that you cant really run away from windmills as they are producing more than half my total energy. also it doesnt make sense to connect cable to sand when you can use windmills to save steel and space. disadvantage is that those sand built this way are dependent on the windmills next to them and cost alot of steel to upgrade.
dont think of underground passageways as just something to transfer resources five tiles away. place them next to each other and it becomes a road through mountains and forests so it gives you some flexibility to use areas that are otherwise blocked by trees and mountains.
Played the second part but need an ending to round off the storyline something like one man's crap is another man's treasure. and maybe some different graphics and stuff for the second part of the game.