I like the art of the menu and the music, though it is a bit loud, but I understand it's not easy to universally tune the volume.
Not having a tutorial in-game is a bit annoying, but time is low so it's fine too.
Some of the sprites look stretched, for example on the UI itself.
When there is a cell on top of a tower, it feels like clicking on it doesn't always register.
Maybe a better indication for what each cell type does would serve better. Even after I read the mechanics, I couldn't understand them.
I really like the music tho, simple and not too repetitive that it gets annoying.
Overall pretty interesting, good job making this in such a short time, I can see you focused on the mechanics. The concept is really good too.
Keep making games!