I believe that the most important thing for a puzzle game is to be clear and to ease the player into its mechanics and this one does it well. I am usually terrible at these kind of things so i don't mind a slower pace at the beginning which is why i like that all the mechanics are introduced level after level, gradually getting harder and leveling up with the player's skills. While it is true that the art is minimalistic i don't think it's that big of a deal since the genre itself doesn't really need too much to work. One thing that could boost replayability could be some sort of timer for the level to try and reach the end of the floor as fast as possible! But maybe that's my action junkie brain in action