I played the game in the Web browser. This is just from the point of view of a non-game who has never played this type of game… The music matches the game very well. The attack feels pretty snappy. I enjoyed seeing the visual effects of the attack. I just kept clicking the mouse and used WASD occasionally, and I could defeat the boss in the second trial. Wish it did not take so many strikes. But, since your game is about boss fights only, I guess it has to be this way. The surrounding rock walls could use a shader that will make it somewhat see-through when they block the sight to the player character. There are two health bars on top of the screen, which I could guess which one is the player/boss. But I am not sure what the bar at the lower left corner of the screen is. Oh, and I am not sure what the Q and E do. And for the purpose of playtesting, it would be nice to have a replay button or something to allow replay without having to reload the page.