First off, nice to see another Monogame devloper!
I dig the style, good shaderwork. I got a very violent and shaky effect on all of the terrain walls, which made it kinda twitch and straining on the eyes to play. I don't know if this is intentional or a bug, but I'd suggest just having the pattern as it is when you stand still.
I dunno if the game window is supposed to be able to be resized, but it started in fullscreen with just a tiny game window up in the left corner. It was very very difficult to read the ingame text.
The tutorial part stated the swap, combine and recycle, but still after playing it a couple of times I'm really confused at to what those commands actually does?
Gameplay was alright, like the concept of battleroyaling yourself to the new level. Also, lightning minigun is OP.