Very challenging and very fun! It had me focused all the way until the end. Very much feels like it was playtested a lot.
-I think the collision boxes for the moving yellow platforms can be longer to match the sprite or the collision can stay the same with the sprite being shortened.
-On level 9 the red falling traps activated even though I wasn't within the vicinity.
-On the last boss the music from level 14 was playing along with the bumblee song.
That's all I got, but I had a few friends play it and they tapped out around level 3-6 due to difficulty. Maybe add 5 easier stages previous to the current first one?
I had a good time though and since difficulty was your goal it sure worked for me. Improved very quickly after a few tries.