Pressing F12 killed the map editor

I accidentally pressed F12 while working on my map. It brought up the HTML editor (or whatever it is called, I don't know its name). It caused flickering, every edit I did made the site reload itself, and now my has no color and the thumbnail has been replaced by a black box. I can't even start editing it again. I don't know what caused this, I did not press anything else. I never had issue with Inkarnate before.

My browser is Vivaldi, computer system is Windows 10.