That's a great variation of the game. Thanks for sharing the page. It's a gem!
If you never have to guess there must be one more strategy to figuring it out I've never seen anyone mention, because I frequently get stuck with two options on the very hardest difficulty.
One non-obvious strategy is that the number of mines that are left on the field is known. Especially near the end, this can break a tie between two patterns of mines.
I thought of that but it hasn't been enough for me. Or I'm bad at counting
I love these kind of webpages with little programs to discover.
The first thing I install in every Android device.