This looks quite good. While it is clearly a work in progress, I can definitely see this becoming something pretty special.
A couple things work noting are that for the background, I'd recommend making it a sort of jungle setting, as that would explain all the bamboo (well, that and the Nerdy Teachers YouTube tutorials), and you could contextualize the sand on the ground as stinky honey, which would explain why it slows you down and makes you jump lower.
Additionally for music, I'd recommend looking at Pico-8 Tunes Vol. 1 & 2 by Gruber. The songs are free to use and quite easy to import into your game.
Overall though, a great showing so far, and I'm eager to see what the game comes to be in the future.