Actually, the hardcore is not that hard. The difficulty lies in the accumulation of crisis cards, and most crisis card can either generate more crisis cards, or spawn a even harder crisis when unattended.
So my strategy is the same as normal mode (rushing out renewable energy, science funding, wind turbine), with the exception of getting social changes card too.
Next, i wait for the second tipping point to trigger. By then, i should be able to dispose 20th century industry and have the resources to resolve the 2 crisis that it bring. i abandon that card, resolve the crisis, and throw away the social card given from the crisis.
If I cant survive till then, then there is not much to say. it is quite rng based on the crisis you get.
In this way, my energy should generate at 54s a round, and my social 80s a round, after discarding the 20th century industry cardx=.
After resolving the 20th century industry card , i dont even need to focus on the sectors anymore. most crisis at the start provide cards for the sector. Their distribution seems to be mainly in Ecosystem, industory, science and people. So unless you are getting all people cards, then maybe you will want to discard some of them to prevent world hunger crisis.
So at that point, I just look through the crisis card, focus on resolving the ones that spawn harder crisis, follows by the one that spawn more crisis, and the one that remove cards and/or resources, and finally the one that add carbon(pollution?).
Really, having a +70 carbon(pollution?) per round crisis is not a big issue, when you have 1 emission clearence and 4 carbon capture. I do have to resolve it at the start, but after the cost rises to 10 people resources to resolve, I just leave it at background.
So yap, I spent 30 min, 5 restart and beated hardcore in one hours total.