Hello, just a stranger browsing the game jam page!
I hope you had a great time working on (presumably) your first game. Maybe you don't think what you achieved is impressive, but there are quite some elements that I enjoyed. Firstly, I like the way you choose to implement the theme. Taking these specific stories meant that it would be difficult to find pre made art, but you stuck with the decision. I also like the fact you didn't choose the most obvious stories (I hadn't heard of Kolobok before this.)
The controls are still rudimentary, but there are some surprising things you did implement that many people wouldn't have. I was impressed with the snap-on you have when just barely reaching the top of an obstacle. I know from experience that those can be a pain to get right, and although there are a few unintended side effects, it works great. Each time I jump into the top of the block, it snaps without feeling clunky. For the rest of the movement, you would have to go in depth on what game developers do to make games such as Celest feel so good to traverse. I suggest https://gmtk.itch.io/platformer-toolkit for an in depth look at all those elements.
And lastly but not least, you have a quit button. You won't believe how many game jam games forget it. It's not surprising, since in the editor and when you built for web, it's not necessary. And (on windows) you can always press alt+f4 to force quit a program. But being required to do that always feels very unprofessional, and that you avoided by remembering to implement it.
If you want to improve the game more, I would also look at implementing a music manager. If you don't want to figure it all out yourself, there are free tools available in the Unity Store that can make the process easier. This would allow you to have the background music play through a scene transition, and not have it restart each time. That is something you have to watch out for. Your game was short enough that it wasn't an issue, but in longer game poorly implemented music can make the game a lot worse. Repetitive music can become grating, and people will quit playing your game out of annoyance. So that is something to watch out for.
I hope you can make good use of my comments, and have lots more fun programming games in the future!