Cool game. I like the polish touches but there are rough edges.
I recommend doing something about the main menu responsiveness. The button presses feel so slow and sluggish that I often feel like I press the button and nothing happens. Also, the lack of highlight when mousing over the button makes it feel like it's broken. The highlight is obviously there but when it doesn't react to the mouse input, it just feels off.
Forget to communicate that you can rotate the rooms with a mouse wheel. I didn't see it mentioned anywhere and stumbled on it by accident. It seems to be a rather important part of the game.
I think the boss rooms should be much more apparent. The first time I saw it I thought that it was just a bad room. Like why is there an elemental reward on that card? Since by beating it you win the game, the reward is pointless and misleading. I recommend putting a trophy icon or something like that instead of it if you want to keep the design. Maybe write "Boss" on top of it.
But hey... it has less rough edges than my game :D Good job.