Thank you so much for your feedback!
You're right, some rooms were more fun than others. I actually didn't spend much time designing the levels. I just randomly made some maps, but I will try to change most of them if I work on them again. Also, to change the difficulty, you click the red roll button. I really should have indicated better that it's a button or made it a press key instead. It's my fault for not making it obvious to the player that they should use the mouse xD.
Again, thanks for your feedback, I'm glad you enjoyed the game!