WASD is actually really hard for me to use (my keyboard uses the Dvorak layout). In the future, it'd be great if you could support arrow keys as well.
Other than that though, it looks cute and seems to play well. It'd be nice if play were divided into waves — cycles of tension and relief are more interesting/fun than continuous tension the whole time. (If it already is in waves, I wasn't able to survive long enough to see that; in this case, maybe make the first wave shorter!)
It's not clear to me how it fits the theme or prerequisite (apart from the title).
But all in all, it's a solid game — good animations, nice sound FX, good overall polish. Nice work!