system
Given the following post, respond as if you're commenting on Reddit:
human
[Snowpiercer] Why a train?

Why wouldn't they make some sort of underground shelter and harness geothermal heat?
gpt
Some governments may have done just that, but the train was built by a crazy billionaire as a luxury cruiser.  It wasn't until the end of the world happened and a bunch of stowaways got aboard that the nature of the train changed.

Some become batman, others become the arrow, others build space rockets of dubious efficacy.  This crazy billionaire built a train.