ok thanks kilicool ;-)
Regarding the level, I found three different endings but not the secret ending yet I guess. How many endings are there in total?
I also found secrets like a treasure chest, a kind of statue protected by lasers (egomassiv?) and a girl near a lamp post. Did I miss any others?
Probably because there are double jumps from small ledges that I didn't manage to do to go higher (I call it the Don Doli special double jump lol)
When it comes to endings, I can think of 6 different ones. Here they are:
#1: Normal ending
#2: Original secret ending
#3: No run ending
#4: Golden creature ending
#5: Tower ending
#6: Waterfall cave reprise ending
Be warned that the sixth of these is an extremely evil secret aimed only at the most hardcore of players. Even my playthrough doesn't cover it, as I gave up upon realizing it was going to break me (though the description for one of the parts explains how to get there). I'm not sure anyone will ever get it legitimately, considering it tasks you with performing an immensely tough series of maneuvers for each attempt.
I wouldn't bother trying to get all the other secrets either, as plenty of them are just really minor stuff that requires exploits to reach. I didn't cover all of it either.