Killing Floor is exactly what it sounds like. Okay, no, it's not a game about a floor that eats everything it touches. We call that game hot lava, and it's much less gruesome than this one. No, Killing Floor is a first person shooter where you kill everything on the same floor as you that looks like it might be a zombie. Sure, it may actually be the result of a failed cloning experiment, but if it looks like a zombie and sounds like a zombie, shoot it.
Killing Floor: Calamity is a twin-stick version made for mobile devices. It's still a co-op experience like the Steam version that gamers fawned over back in 2009. This time you're just looking downward as you and a friend gun down everything else that moves. And if you have an NVIDIA SHIELD device, you will get to enjoy better visuals than other Android gamers.
While more of a re-imagining than a port, Killing Floor: Calamity remains a thoroughly replayable shootfest. You can load up and charge in for $5.