This game is not challenging. The stages are actually pretty tepid in comparison with true hardcore platformers. The fact that the stages are really small, often screen sized, collaborates to this. There is only a handful of obstacles on each, no life nor time limits. So the difficulty is around 7.5 / 10.
Things start getting hardcore when Silver and especially Gold ratings are desired, because there is now a very tight time limit and, even though deaths are allowed, they still take time to recover from. Then, the difficulty goes to a 9.5 out of 10. (10 would be "I wanna be the guy").
Hardcore platformers are all about control and level design. I had no issues with controls, and level design was indeed great - It has some sweetspots and shortcuts for the taking (for those bold enough to try their way around them). Examples include Act 2 final stage (fall between spikes) and Act 7 Stage 1 (quickjump to finish level in 6 seconds)
Contrary to the previous review (NeonSpider) I don't think that lives-only method of control would be reasonable because it would favor "turtling" instead of platform action, and would harm (or even kill) the premise to the game, which is VEXATION.
I do agree, however, that avoiding death in this game deserves a reward, or a medal. It is almost impossible to do so in act 8.