Hello! Great job, thank you for playing the game to completion (I deeply appreciate the dedication and patience) and the feedback. That beginning/ending screen is badly designed, it's a 10/10 samples in my heart! Completely agree, the early areas need a redesign as the difficulty curve is all over the place. The wall slides/jumps ended up being the most difficult thing in the game, but also in my head it made sense for that to be the first upgrade as the jetpack would render it obsolete in many situations (although not all of them, as it's a lot harder to control). Originally the jetpack/flamer were designed to have a fuel resource which I had to cut (more for level design concerns than feasibility). The game even had a functional wall jump unlock which got cut to streamline level design. Looking back, perhaps a better order could have been flamethrower -> slide -> jetpack. Sorry for the rant, I enjoy discussing design quite a bit.
Cheers