Short, but well made. The tone sticks with the player, in a big parts thanks to the music and enemy design (both sound and visual).
The mechanics are explained well on the game page, pity there isn't a How To Play inside the game.
Funnily enough, because of this I have tried to finish the game almost pacifist-style, without ever attacking, because I didn't know I could attack (or heal myself, for that matter). I've managed to almost get to the last room that way.