Really enjoying playing this one! The level numbers seem to be going up by 2 though, what's up with that? In any case I'm up to level 40 (or thereabouts) and I do have two suggestions:
1) Any chance of adding a menu option to jump to any arbitrary level?
2) There seems to be a bit of a balancing issue, levels suddenly appear that are way more easy than levels that appeared before them. I don't like giving constructive criticism without suggestions of how to fix the issues, I guess my only suggestion here would be to get some volunteer testers to grade each level on some kind of scale and rearrange them accordingly?
I do like the appearance of different mechanics as you progress, the most notable ones so far being the introduction of the ladders and then the arrows. Looking forward to seeing what else you throw at us in future levels.