Notes on this puzzle
40 mines, 216 safe cells and one 16×16 field: that is Mine Finder #5207. Some cells only give way when two neighbouring numbers are compared.
The board starts with 52 cells already uncovered, 24% of the safe ground, so the first deduction is waiting for you. Under the cover, 55 safe cells touch no mine at all, 101 show a 1 and 45 show a 2; 15 cells carry 3 or more, and the highest number in the field is 4. 14 of the mines lie along the border of the field. Corners hold 1 of them; a corner cell has only three neighbours.
Where to beginWhen two numbers share most of their neighbours, subtract one from the other.