Haven't finish the game yet, but i noticed there is a 'bug' where you can't see 'items' throught this glass walls, if you look closely, you can also see that the walls become invisible too. If that is an intended mechanic, i'm not really fond of it.
Game is really fun and the sprites are really cute and well made! There is one thing that i would like to point out. The birds can leave screen making it impossible to pick them up.