I like the art style a lot! Portraits in the mirror are a really fun indicator of remaining lives. The music track is very fitting.
The controls are perfectly fine, I just think that the game needs to visually clarify what you're doing. The purple target points are probably unnecessary in the defense phase, having the stalks light up before firing would be enough. On first play it feels like the targets are what I was meant to be interacting with or trying to time my hits at the point where a stalk reaches a target. Attacking one side at a time can also be clarified by showing slashes and having them appear on the wrong side when the mirror is positioned incorrectly. It took me too many tries to understand the offense phase, because the description makes it sound like I'm searching for a specific hidden point rather than just moving the mirror to the center of the eye. WASD as an alternative control scheme may also be a good addition.
After knowing all of the mechanics the game is quite fun! With a few visual hints and a slower start, I think the overall action can be made longer, faster and even a bit more challenging.