You've got a nice-looking well-structured puzzle game, the level design and how it gradually introduces mechanics and expands on them is really smooth. Sometimes it feels like a guessing game whether or not your friend will hear you, but nothing too bad in any way. Also, when using boxes that you have to push consider that players can corner them and be unable to move them again (it happened to me), you can consider adding the option to drag them back or a way to reset the box's position.