Just 2 suggestions: there is not much to do when you can play and be online a lot. So why don't make upgrades cheaper , tweak them to be less efficient, that is how players will be attracted to stay more time online. The same thing with depletion of fuel cell, make it faster, staying online will be rewarded. :)
Idea / Suggestion: To be able to manipulate heat amount transfer for each side if the heat exchangers. For example tell a heat exchanger to transfer 70% of the heat to the bottom side and 15% for left, 15% for right side. Also you can restrictions to directions of the heat transfer - for example heat should be only coming from one side , and pushed to the other 3 sides
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