If "Metro Exodus" were all about trains, it could be a game like "Keep It Alive". As a train driver, or rather a shoveler and guard rather than a driver, you are present at multiple spinning plates as the train moves from station to station around the world.

First, there is the engine, which must be kept full of precious coal at all times. Otherwise, by moving to the right side of the screen and alternately hitting left and right in rapid succession, a zombie-like creature will board the train. When that happens, you must jump in the middle of the train and shoot bullets into it. Both coal and bullets are limited in number and are only refreshed between stages.

When not feeding the train and keeping the zombies at bay, you must keep your heart beating, or your cargo alive, by turning the handle frequently. It's a tense, fun game of plate-spinning, but the ending is a bit too silly. However, this is a fun piece of post-apocalypse side-splitting.

For more great free experiences, check out our roundup of the best free PC games.