Okay, that's very good to know, thanks! That is one of the biggest problems with game jams. Making sure the difficulty curve is smooth enough while always knowing the solution.
Viewing post in Count Your Steps jam comments
My first thought to mitigating this would be to ask some friends beforehand if they could playtest a version of your game without all the polished stuff just to see how the level design and difficulty curve are. Of course this is easier to say than to do, but I think its worth a shot in the future :)