First impressions, this is very cool!! I was already enjoying the design of the tutorial area that eases you into an understanding of the game's controls. The introduction of the Sludge World as a reality shifting concept is wonderful and caused me to give an audible "ooh!!" and the music changing is a really really neat touch that adds to the whole appeal.
I like the main character's design! While somewhat basic, the addition of the flowers and vines add a lot to the design and the general theming of the game.
My main complaints arise in the game's main level. There are frequent instances of 'leap of faith' jumps where it can be very unclear where the ground is going to be and, if it is there, where an enemy might be which lead to an unfair death or two in my run.
Regardless, this concept shows promise and you've done very well to bring it to fruition in such a short time! Well done! In the future, I'd love to see further updates with more attack options (while moving?), enemy variety, and stages!