This game has moments that feel great, when you get your grapple spacings and timings just right and are able to fly up and up and up, constantly slingshotting yourself up further with the grapple.
However, I think there's a handful of things really holding this back, the biggest of which is the camera. The camera sits much too low relative to the player. Much of the time, jumping and grappling upwards sends your grapple slightly above the screen, meaning that if you're the highest you've been, or you're trying to go up as quickly as possible, you are quite literally firing blind. This really puts an immediate halt to any momentum you've built up with the grapple, and is also just generally frustrating.
Another issue is the lack of sound - I think just sound effects for the grapple, the jump, the super jump, and landing would be more than enough to breathe more life into the game alongside some music.
Frequently I found myself making it as far as I ever had, having felt like I had improved at using the grapple and making it to a new high much faster than before, only to be shut out entirely by the fact that there was absolutely no visible platform anywhere near me, and I was resigned to blindly shooting my grapple up in the hopes of hitting something, and then simply waiting out the timer anyways.
While the scores creating new platforms is really interesting in theory, in practice here it amounted, for me, to forced repetition and frustration. My high scores didn't feel earned, because I could simply do it all over again in the same way but get farther because of my last score. I never felt like I actually reached a "high" score because of this - I wasn't getting farther because I was getting faster, or improving at the game. It was just, well, there's another platform in reach now, and there wasn't one before. This was made worse the higher up I went, where the naturally-occurring platforms got more and more sparse, leading to sometimes two or three separate runs before I made it to another black, non-score platform. For a high score game, it felt like I would never be able to keep a high score, since the next decent player would just use my platform and outscore me anyways.
Since the game is also all about moving upwards, there never felt like there was a good reason to do anything other than grapple straight upwards. Occasionally the super jump was useful to put me in range of an otherwise out of reach platform, but again, there's almost no way to know there is a platform that high up because the camera stays too low. The super jump itself also felt inconsistent. It was definitely higher than a regular jump, but doing repeated super jumps occasionally sent me much higher for reasons that I could never quite pin down.
Also, I think the UI broke after my first couple of attempts. The UI for entering the initials was blank, so I couldn't see the initials I was trying to enter. Also, I could have sworn there was a number that showed how high I was next to the meter originally, but it also quickly disappeared, and reloading the page didn't make it come back on the web version.
I would love to see a version of this more akin to a platformer, rather than an endless jumper, with these grapple mechanics. I think they have a lot of potential when there's more to explore, rather than solely going up, as that would give the player a reason to use the grapple diagonally or sideways! The grapple mechanic itself is a lot of fun, and works so smoothly.