Thanks for playing and your your kind words! Yes, we were aware of this bug with stuck chestnut on top of garbage can, but we decided to ignore it ;-) About how the game is connected to the theme we left two hints. Theoretically the main one is the intro, which probably is not as self explanatory as I thought. The second one is the description of the game on it's itch.io page - I'll paste it here now:
"[...] young person unaware of the consequences litter in a nearby forest. The forest spirits, angry with his actions, incarnate him into a squirrel named Chestnut to show him that the place he treated like a garbage can is someone's home. To redeem himself, he must clear the forest and help his tribe of squirrels collect chestnuts for the winter."