Took me ~15 minutes to finish the game with all 8 pearls. I will say that it is really good, and very well polished. I will say one thing. The mushrooms are such an annoying game mechanic. If they were intended to be so frustrating, then developer, you did a really good job. The mushrooms became the "enemy" that made me lose the most.
As a platformer, there isn't much for me to critique. You did well with the movement, the wall jumps were handled excellently, and the jumps felt constant and natural. My other small complaints was that the pufferfish collision was weird at first, but then I got used to it. There was one really frustrating section with the moving fish and three sea urchins that got me stuck for a while, and I almost gave up until I saw the "almost free" text.