The hidden levels increase by 1 each time

That 1 level up isn't just a simple increase... It took me 24 rounds to get to the previous hidden level, so I wonder how many rounds this one will take... Still, it's been months since the last hidden level, so I'm playing hard. I feel like I'm going to get arrow-induced sickness.. Don't stress about the ads; just close the window and restart the game, and they'll disappear.