I really enjoyed the first 20 levels, you did a great job with an interesting concept, but pixel perfect jumping while timed in the later levels is just not fun for me.
I like the look and feel of the game, but it could be a better game if it was keyboard controlled. The logo tripped me up quite a few times, coving the game play area, and I found myself trying to not click on it.
for the levels you don't like, 1. open the level and loose it, 2. click the in game "Back" button twice, 3. open the the "Instructions", 4. click the "Video Tutorial button" 5. while following the instructions, you will see the level number that you do not like in the corner, and when it is done, the level will be marked complete.
If you are going to make endless mode "harder with enemies getting exponentially higher HP and damage", you need to make the coin return exponentially higher as well.
Glad to know I've upped the pace a bit ;)