I like the pixelart shader! I think the game looks pretty confusing at first though.
Thanks for checking out my game!
It's actually not a shader, gamemaker draws things first to a thing called "application surface" which is (what I understand)just a texture then later on drawn on the screen. and by changing resolution of that surface( or texture ) you can achieve pixelated look.
I'm pretty sure that you can achieve same effect with unity pretty easily too!