It's a speedmap. 

Flames designed the map with speedrunning in mind. He's done a great job... And it has a real vanilla feel, he's also done really well to jam all those secrets in such a small map. 

I did play this after seeing GGRC post a video about it. I'm not big on speedrunning or the lack of detail in speedmaps, but this one was alright. I did not get an impressive speed but managed to kill everything after finding all the secrets.