Beautiful game. The music is awesome as well as the character design. The story also quickly pulls the player in. Looking forward to play the full game. Below is my nitpicky criticism, as a fellow developer working on a game with similar gameplay elements.
- Scene transitions feel a bit abrupt. I think a quick transition effect will make the game seem more polished and professional.
- The path to the apple tree, also the path to the ring feel a little bit too long. This is because new gameplay mechanics, enemies, or even new tiles/decorative objects are rarely introduced. Almost all scenes were probably created with a limited number of tiles, and it shows at times.
- There is no incentive to killing enemies. Rolling through everything to get to the goal seems to be the optimal strategy.
- The player cannot walk behind cliffs. This might be a design choice to avoid occlusions, but I think it subtracts from the illusion of height difference.
- Wasps can fly through cliffs, but since they don't actually change their height, it looks a little unnatural when they do.
I am pretty sure some of these things are already on your list. As I said, these are really nitpicks, and I had a really positive experience playing through the demo.