That's crazy for a game jam! It plays super well and looks great. Definitely true to the jams theme and nice use of colors. I also like the more slow paced movement compared to most fast paced platformers nowadays (that's just preference though).
The only thing I can complain about is the difficulty having a huge spike towards the end with those flying things (with the green color palette). I didn't die until or after that point, but at least 10 times there. But maybe that's just me. :)
How many HP boosts are there? I got 7 hearts in the end.