Here's something weird. The very first time I tried playing this game, and once again since, on starting the game I could see every mine on every screen (so there was no challenge and I could just walk past them). Every one of them appeared as a solid red character square, rather than being invisible.
Yet when I start the game again now, all the mines are invisible as expected. I presume I must have pressed something accidentally on those two occasions when I saw the visible mines, and activated some sort of cheat mode or debugging code. The question is… how did I do it? What did I press to turn this mode on? Certainly, it ruins the game in terms of the challenge, but it's also interesting in terms of letting you see a lot further ahead!
This was all on the original release, not the recent bug-fix… but I'm guessing it's a deliberate hidden feature rather than a bug, so hopefully it's still there to be rediscovered.