I liked the style of the visuals :) . Although I dont think it fits in the boss rush game type but is a good game.
Also there is a couple of bugs I would like to report. When you die when the player is holding dust you cannot pick it up anymore. And i found some strange interactions with the pause of the game: When you die you can still pause the game in the game over screen, in the third level the game starts paused and you have to press Esc to play.
Finally there is an error the layer order in the third level, the dust appears in front of the player.