It sure looks nice. I had a few problems with it. For one, there seems to be only one enemy type. This isn't necessarily a problem, especially since this is the low effor jam, but I really dislike the one enemy type this game does have. For one, it doesn't fit the art style. Secondly, it has way too much health, and thirdly, I think the idea of an enemy that multiplies when it's killed is conceptually flawed, as it thinnens the satisfaction you get from killing it.
Another problem I had was the predominance of impact freeze-frames when wielding the sword. Impact freeze-frames are a great way to show how powerful an attack is, but, in my opinion, you should only use them to contrast strong attacks from weaker attacks or in games where you can kill most enemies with a single hit. After a while, it just gets annoying.
Not sure how well this fits the theme. I guess there are monsters, but nothing really screamed "spooky" to me.
I really liked the final boss and thought it was really well designed, but I only managed to beat it because I got very lucky with the number of empty rooms I got. One more slime room and I would have gone insane.
Also, I don't know if this is supposed to happen, but when I beat the boss, it just disappeared and I was left in an empty room.