Still wondering how the whole of humanity wound up on a giant train in the middle of a frozen wasteland? Bong Joon-ho's latest trailer for Snowpiercer and CG backstory video explains (almost everything).

What happened:

Snowpiercer is set in a future where, after a failed experiment to stop global warming, an Ice Age kills off all life on the planet except for the inhabitants of the Snowpiercer, a train that travels around the globe and is powered by a sacred perpetual-motion engine. A class system evolves on the train but a revolution brews.

And here's a collection of character videos.

Still no idea when or how this movie is coming out, we're thinking 2014. But we'll let you know the second we find out.