Nice entry, the game is totally in the theme. Since I don't see much menu good job for it too !
The ambience is pretty cool with those graphics & music, it feels like a horror mansion =3
The gameplay is simple but fun, it would have been nice to add some new mechanics over the waves (other way to spend our money) since it feels a bit redundant after some waves or maybe punctual power up / events.
I think lowering the mouse speed could help to avoid player doing the "swiping no justsu".
A small feedback when you missed an enemy could be a nice adding (like a small red blink or ...).
Great job for your entry !