For your first game this was incredible! The art was really good and I was impressed with how much level design you managed to do, and how good it was.
Like you mentioned the main issue is a lack of sound, but it's always hard to make time for in a game jam. I would also say you should give the spikes more contrast so they stand out against a light background.
Other than that I thought this was a really solid entry and a great first game!