I like the concept of switching between night and day and how the mood changes with the transition. I also like the environments and the lack of shadows gives it a unique look.
I did encounter a bug where I got stuck and was unable to jump out, forcing me to refresh.
It was also visually unclear that I could jump on this spot. I wandered around a bit wondering what I needed to do before I accidently jumped on this.
I would also suggest indicating that the pickups change the environment. At first, I didn't realize the things I was collecting/interacting with added new objects to the environment. It took me a bit of wandering around the first area before I realized that the vine by the desk had appeared. Not sure if it was lighting the candle or collecting the plush that activated it.
Besides that, nice job on the game! I enjoyed the visuals and the concept has potential if you add more variety in puzzles and interactions between the day/night states.