Really satisfying to play, and replayable too with both the secrets and the upgrades to change things up.
The pre-game infodump is kind of rough since it's a lot harder to take in information about a game you know nothing about. I personally had to restart because i skimmed it and missed the pull-up system.
It also seems kind of redundant to have both level-dependant upgrades and secret-dependant slots for them - at least for such a short game.
Those are really minor things though. Enjoyed this one a lot.