The thing that sets the game apart, is that you can create your own levels and then share them with everyone. Of course, I believe that ability is behind the paywall (I think, don't quote me on that) as you have to pay their coin version or whatever to be able to share a map you make. I think anyone can go and make a map, but only those who pay can either save it, or share it.
Either way, it's a fun little game. I don't know what anyone was expecting with it, but it was more or less a Minecraft clone with an actual FPS involved. The devs listened and added a lot of stuff in the launch version, hell they added turrets!