Hey, good job!
The submission is elegant and you managed to fit a very challenging set of constraints between theme and limitations.
The art and music are great, the space you have for improvement is in the gameplay: the game is rather easy, and could benefit from a difficulty curve (perhaps using a wave format, similar at the one used in tower defenses, and perhaps you could "earn" the usage of chocolate rain.
One last thing, that is a generic advice to anybody doing games in Unity: build to WebGL! it simplifies the distribution (instead of 3 individual builds) and itch supports to play directly on the website.
Overall, a very solid submission! good work!