The physics of flying off the mushroom are fun. First-person jumpers are difficult to make work because the player doesn't have a sense of what their collision capsule looks like, so has to chance it every time, and it's easy to fall off and—in the case of this game—have to restart at the very beginning, which makes the loop a tad-bit tedious.
Zany music matches the art style, so there's great tonal consistency there. What makes the environment pop are the animations of the mushrooms, and the leaves growing out of the trees. Excellent work there!
I would've liked a more clearly defined goal, as although I did figure out the objective of the game was to climb the tree, the player motivation for "why?" was undeveloped (and saving an unseen character seemed a lazy / uninteresting objective). Then when I kept falling and restarting from the bottom, I hit a loss condition somehow while climbing up the tree again (so I presume it's tied into an unseen timer, but if so, these gameplay-affecting metrics should be represented either in-game or on the UI).
Good effort with Infinitree!