Thanks! I don't even know how to reply to everything correctly :D
First of all I'm really glad you like the concept! :)
I was not sure if the "spherical/circular side-scrolling platofrmer" would be generally likeable but I couldn't really name one game with it and really wanted to try making a game with this idea.
The original idea was one circular underground gameplay with a central gravity and a giant gemstone or something in the origin the player has to mine. - While getting the needed equipments, exploring...etc.
One big map felt difficult to design very well because I've never tried to build a level that's spherical and somehow I thought scaling it up into multiple smaller planets, even travelling between them could be a good feature which basically became the overworld / open-world segment of the game.
As for the controls I couldn't make the jumping itself good yet...I had some problem it, like accidentally jumping out from the gravitational field of a map and getting stucked in a point in open-space. - It's still a remaining bug or rather glitch that can be reproduced.
The main problem is that if you jump, then move right away it "drags" the player down right away so basically the jumping only works when you are standing in one place without touching the movement keys.
Fortunately implementing this simpler grappling hook made it much easier to traverse spherically, but as you said the controls still could use an overhaul.
As for affordances the one I implemented so far is the compass that's rotate in a way so you can always see which direction is north...etc. Still I can see it's not easy to navigate, I'm thinking about a minimap or something similar that shows the planets, areas. I've never done any minimap in any game so right away implementing one for this kind of game would be certainly challenging.
On your screenshot you are supposed to shoot with an equipment you can find the button next to the wall you got stuck in. The button itself is...not very visible or contrasted relative to everything else and I want to redraw it or highlight it somehow, maybe in the next update. - It has another bug as well...basically turning off/on rapidly if your projectile touches it more then once so it's also hard to simply press it.