The important thing to mention is that your influence on event 2 can change the options available to you for event 3.
This system seems unique to me not just because time is a factor, but because an entire civilization is at stake and influences the story, not just one character. A choice you make may determine how many people survive an event, which in turn influences the next event that is contingent on how many people are traveling with you. As the player, you'll have to decide whether it's acceptable to let people starve, or be left behind, or to sacrifice a few for the many. We don't tell you what the good or bad choice is, it's just a matter of what you feel is right.
The last thing to mention is that this does mean the finale is largely in your hands. I can't get into too much detail now but as you can extrapolate from what we've talked about here, your options during the finale will be a result of your combined decisions, not one of three inevitable choices.
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To mention it, we are intentionally trying to make it so that there is no "best" path where you save everyone. But more importantly, like real life you don't necessarily know what the best path would be anyway. You may save half a town and wonder if you could have done better. If a town drags their heels and takes days to pack up and leave you may not know how that is going to affect the next event. It definitely goes beyond "saving people", however, into the realm of ethical dilemmas, revenge, no-win scenarios and everything else that comes with the end of the world. We're in love with the idea that you accept the result of your actions and keep going.