i didnt do the fifth page of medium difficulty in the beginning of the first map. i stopped trying even if i almost did it. Is that correlated with i wanna be the guy? haven't played these games so far.
Remains to be seen if glass coffins become popular.
There's about 10 pages per world, each of which increases in difficulty, then 10 worlds (iirc), all of which increase in difficulty too. There are also boss fights along the way. I've played for 5 hours now and only got to the fourth world on medium difficulty. I'd love to see someone do it on "you're gonna get raped" mode.
EDIT: found out this developer solgryn also made something called "Wings of Vi" if that is at all related.