Thank you for reviewing my game. I completely underestimated how difficult my game is. By the time I noticed (was told by players) I had no time left to add a checkpoint system or make it easier :( Once the rating is finished I will make an updated version with checkpoint system and maybe even a 2 key version? Not sure yet.
I've been there, so I can understand. By repeatedly playing the same level while developing I generally forget how difficult it might be for first time players. I faced the same issue with my first jam. But thanks to feedback from other participants, I realized this point. So now I always reduce the difficult a little bit before submitting. You can try this trick in your next game :-)