I loved this! It's so creative and cute, and the reload mechanic turned out to be surprisingly fun.
My only complaint is that after a few waves, I thought the gameplay was a little repetitive. I like games to be quite hard, so the difficulty may have just been a bit undertuned for my taste. I quit after completing wave 20, so I could see what the twist was.
Any of the ideas you've mentioned in other comments would help mix things up, especially if something new happens every 5 waves or so. There's so much potential to add creative things onto a simple idea, which I think is really cool!
A great entry that brought me a lot of joy; well done!