It was an early access game that hasn't been touched in a few years, presumably abandoned by the developers? "Something happens" and you find yourself sucked through a portal on a train going through the void with creatures that can attack you.
The gameplay loop is pretty similar to Raft, you spear things from the train until you make it to the next station and upgrade. There are creatures that can help gather and automate some train management tasks, but all in all it was a bit .. boring? until they add purpose and a quest other than upgrading.