Ok, this is really cool! Very creative idea for a tower defense game.
For the camera, I found WASD more intuitive than dragging with mouse. But I think it might have been better overall if the camera was top down, and the walls and towers made taller for visibility. Or maybe just a really wide angle camera.
Another feature I kinda wished I had is the ability to destroy towers. Because once they take place, you can’t place your light there anymore, and its possible to fail just because of tower placement.
I would love to play a fuller version if you ever decide on building on this idea.