For your first game, this has some good stuff! Especially considering you joined a jam with a time limit for creating your first one. I really like Steve and his sprite and animations - did you do them yourself?
Now, of course there is some lack of polish, the platforming being really floaty is unfortunately what in the end kept me from finishing it - I couldn't get past the section, where you have to use those fast moving vertical platforms that are embedded into slower moving ones with spikes.
But don't give up, to keep with the theme of the jam, for a first game made in a week, this already has quite a lot of promise!