I love that you have a README and License file (main criteria for open source category). Nice clean and well organised repo; good use of screenshots in your README too.
I love the 8-bit cat graphic (logo), super cute! Platformers controls are super hard to get right, and you've done a great job (jumping seems to be slightly inconsistent), and the movements of the mouse are a little inconsistent too making it hard to time the jump. Your game would probably benefit from starting easier and progressively getting hard and introducing enemies etc. Great job and I enjoyed the art-style and chill music. Maybe add some sound effects for even more immersion. Nice work on your game, I had fun playing.