Thanks for playing and for the feedback!
> I was curious if the dirt/grass, blue, and yellow walls would react differently, but it seems to just be an artistic choice
I agree. If there's a single thing I want to smooth out, it's that. I lost my way with the yellow. (I'd never made a tileset before and decided that 1 A.M. this morning was a good time to do so.) I already had the levels designed and knew that there were a few spots where I wanted to lead the player to a particular platform. I kind of abused it when applying the tiles, though. Maybe it shouldn't be yellow. If only there were more time!
> I struggled a bit with how you have to already to holding down A or D and then press W to jump up and over. I died several times because I'm so used to AW or DW at the same time or W then A/D working.
It's a conflict for me and I struggle when designing those interactions. I tried to keep them to a minimum. If my live-in play tester – who only plays casual games on a tablet – can't get through it, I typically redesign it. This time around, it was smooth sailing. I'm not sure what the alternative could be. Maybe the player avatar could jump automatically, like Zelda: Ocarina of Time?
> I was tempted to quit on the second or third whistling level where you have to immediately get out of the way.
Do you mean this one? I think you're right. I'll make an intermediate level.
Thanks again for the feedback! I really appreciate it!