Very fun chaos game. The jump height being random here certainly turned out to be an interesting challenge, think it took me until the ghost castle to fully realize that was the gimmick. After having played Cactus Block, that game helped me to realize the fun in an intense RNG factor like that. Sometimes I'll boss through a level and sometimes I have to fight sylvie's legs to survive, and I thought that was somewhat engaging!
Most levels use predetermined enemy patterns, but some, especially some secret levels, have random patterns as well, contributing to that theming well, Volcano Hellcavern being an early test of RNG endurance (and special for showcasing sylvie's incredible feat of lava swimming (or, is that water framed at sunset?)).
As another commenter pointed out, each level needs to be tackled in it's own way, some you gotta be fast, others you need to wait for the right opportunity, some you gotta go fast then wait, and some are about survival, it's a decent blend for the short runtime, alongside the variety of visual themes, particularly in the secret levels.
The Sylvie Shop is a fun and very welcome inclusion, including the incentive to grind harder levels for the things you need. It steers the game more towards being fun and trolly rather than frustrating. I ended up clearing most levels without items, but Castle In The Sky, Dive to the Utmost Depths Extreme, A Lovely Flower Field, You're a Fish Leaping At Me Extreme, and One Last Summer Finale Extreme ended up a bit too extreme, so I used them, with hearts definitely feeling the most worthwhile of them due to deleting foes.
The sounds all being self-made (I presume) vocalizations is something I've done for one of my projects, and it's delightful every time I see a game utilize that modus of sound design. This game is top tier in that regard. My favorites here include "sylvie!" "thanks!" "melone!" "ooooooooh!".
(also, it's a little thing, but the protagonist/developer thanking you for buying her items made me feel a lot less bad about buying them, good positive reinforcement!)
My final thoughts are; very silly summer game, me enjoy :). Thanks for all the fish.