As what the others have mentioned, the level restarts back to level 1 whenever you're dying in the game, so it was kind of a letdown, but as for the challenge and artwork it is simply great.
Regarding the difficulty, I find it challenging not only because of the level design with the spikes/stakes, but especially with the bat's jump. By having its jump strength consistent, the player must be wary of their surroundings when navigating mid-air, in short, the player have to time it right whenever they lands off and on.
Overall, it is challenging, and it follows the limitation well.