Thank you for the feedback, and sorry to hear you had a negative experience with the game. I'm a solo dev and found out about this even rather last minute, so I've been struggling to get the game in a state that works well as an open-playtest in time. Worse yet I realized that the web version you played skipped the introduction to the game, which should have eased you better into the game rather than jumping straight into the deep end.
- As for sound, I just haven't had time to source and implement this, but I'm hoping to do so over the next week or two. While sound isn't 'crucial' for the game to function, I do understand that it (and the lack of it) can greatly diminish the experience.
- The walljumping mechanic is something I need to better figure out. The intent was to try to introduce it in a way that players would understand but from most playtests this seems to be a drastic failure. Part of this is an issue with lack of feedback the game gives, but part of it is also just that it works in a particular manner that is somewhere in between the two main types of walljumping behaviors in platformers. In any case I'm going to be iteratively overhauling the mechanic and how it's presented to new players until this problem is addressed.
- There are various issues regarding the web build of the game as you surmised (such as the mouse cursor). The web build was really only made as an ad-hoc way to run the game without the need to do so through steam, which currently is using a closed playtest