What a fun game! I'd say it's off to a great start. I'm guessing there will be treasure chests and items in the tower eventually, that would add some texture to the game play.
I would recommend a hot key for the climax attack. I'm playing in a browser in windows, and getting the mouse to the button quickly seems a bit odd.
Also I noticed that pressing the space bar seems to rebuild the current floor. Intentional?
I'm really liking that it is unique, nice work.