Others have already mentioned that the biggest flaw is just that there's nothing really to do and while I do agree, I think the addition of a clock would have helped greatly. The clock would give you an easy way to know when sunrise is coming and for how long until sunset, but it would also help you keep track of the days.
Just that one touch alone would immediately convey how futile surviving for an extra day is when the world has ended. It's a solid game with nice pixel art and I didn't really notice any bugs. Good job.