The square at coordinates x=3, y=0 counting from the top-left cannot hold a mine (the one next to the 2). Try to assume a mine is there and calculate where the

The square at coordinates x=3, y=0 counting from the top-left cannot hold a mine (the one next to the 2). Try to assume a mine is there and calculate where the other mines would have to be to satisfy the 2 and the 3 below. It's impossible, therefore that top-left square is safe and because you guessed when you didn't need to, you lost the game. I agree that the game doesn't make it very clear why you lost.