At first, it was just a platformer. But when I got that "final jump" wrong and fell down and the music started, even the art felt better down there (not that it was bad above the ground, but it seemed a bit more interesting down there). But even above, I think the tutorial worked well: it wasn't a "read all these things first, and hope you remember which button does what when you actually need to press them
One thing: since it doesn't start by showing an engine logo, I would probably have mentioned on the page (or on the credits screen, if there were one) which engine I were using. I guess that's something you can do after the jam (and if you want to add it "somewhere" before, you could just write a comment on the game's page, I'm pretty sure comments can still be added there even during the rating period.
I'm glad I made it into the cave so that I could hear the music, it was really fun and seemed to fit the environment and the story. And I like that when you fall on spikes you're sent back to a reasonably close location and not far back to a place you were long before. The fast movement made it hard to land precisely though, so I didn't get to see any collectibles.