Things I liked:
I know you didn't create the art yourself, but the aesthetic was super cool, combining the viking imagery with more modern elements created an intriguing disconnect. As other people have mentioned, the forgiving collision for some elements was a godsend, particularly given the floaty controls. I don't quite know exactly how you managed the transition from falling into the pit to landing back on the platform, but it's easily one of the smoothest, cleanest ways I've ever seen that particular transition done.
Potential areas for improvement:
Some of this is probably already in the post-jam version, but I played the WebGL build so I didn't see it. I found the controls too floaty-- if you gave the character just a little more weight so that they came to a stop faster when moving laterally, it would make the game much more manageable. I didn't fully understand your main mechanic involving the button; it didn't really feel any different after the button supposedly broke. I feel like if you gave the button a larger function controlling the obstacles (such as reversing the direction of moving pillars) and incorporated that into the level design, your game would feel more unique and fun to play.
Overall:
The first jam as a solo developer is always hard, and I'm glad to see that you've taken to the challenge with gusto. I'm glad I was able to find this game, I think with a little more polish it could be very fun and interesting. Good luck on your next game, and I'm sure you'll be a valuable asset to whichever team you join!