You can bind a specific key to do that via [Settings > Keymapping > Camera > Reset], or more simply you can just spam the Camera tool hotkey ([Z] by default) until it resets.
Ratings are a massive deal on Steam, so I'm very much intentionally holding the trigger on Steam release, because I don't have the time to take the leap to polish things properly since I'm still doing freelance stuff full-time currently. Releasing a 4:3 resolution Flash game with notable performance hitches there would be absolute suicide. I get away with it on Itch+Kartridge because they have that certain indie charm, and most of the players are funneled through Kong, so the expectations are clearly tempered. Whereas on Steam the vast majority of people would simply judge the game as-is and murder it.
Spirit Level displays angles, and there's a (very arbitrarily-scaled) Try Square I suppose you could use. A lot of the stuff isn't exactly designed around precision or realism, though (see quite a few of the oversized firearms because they'd be too awkward to use with the cursor if they were properly scaled to doll-size.)
 "Mutilate-a-Doll 2"){kind=icon}
 "Clicker Heroes"){kind=icon}
My next game is going to be on PC and web, similar to MaD2.