the only asset I used is the meteoidvania controller from the unity store.
https://assetstore.unity.com/packages/2d/characters/metroidvania-controller-1667...
Its free and I almost always use it for 2D games. I always heavily modify it but its an awesome starting point.
I added the had and changed the animations.
The snowman and house and lights and stuff were all me and google. Nothing fancy ;)