This is a awesome game/demo. I do wish that there was a sprint button, even if it was an upgrade like "Lighter Coat" or something, it would make early game move a little faster. Also a little bit of ambience and/or a theme song would make it feel more complete.
Having a night shift of penguins and a day shift of penguins would be only be good if you added a way to sleep. Maybe being able to go inside of the igloo yourself would be a good way to sleep, which would be good if you only had a day shift of penguins. These two would only be good if they were both in the game/demo together.
These are just suggestions that wouldn't need to be in the game to make it a good game. It is already super fun.