The flag counter does not check your reasoning
In the local edition, placing a flag decreases the displayed counter and removing it increases the counter. That is bookkeeping for placed flags. It does not prove that a flag covers a mine.
Our Beginner session started with ten mines. Flagging the proven square at row 4, column 3 changed the counter from 10 to 9. The evidence came from neighboring clues, not from the counter accepting the flag. A counter of zero is likewise not proof that the board is solved.
Use a short justification before each flag
For every new flag, finish this sentence: “This square must contain a mine because…” A clue with one remaining mine and one remaining unknown neighbor is a complete justification. “It looks like the usual pattern” is incomplete unless you have checked all surrounding squares.
If a 2 touches two proven mines, its other covered neighbors are safe. If one of those flags was a guess, you cannot safely make that deduction. Keep guesses out of chains of supposedly certain conclusions.
Work backward when the flags disagree
Suppose a 1 appears to touch two flagged squares. At least one flag is wrong if you read the neighborhood correctly. Do not open more neighbors using that inconsistent position. Recount the eight possible neighbors, check which flags were actually proven, and remove the unsupported one.
A different warning is a clue needing more mines than there are remaining covered neighbors. That can expose a mistaken earlier assumption. Reviewing the last few flags is more useful than adding another guess to make the board look consistent.
When you still cannot prove a safe move
Scan other revealed boundaries and try overlapping-clue reasoning. If no deduction is available, acknowledge uncertainty. Two covered squares are not automatically a 50/50 choice; other clues and the total mine count can constrain them differently.
This guide does not calculate optimal probabilities for every board. During practice, separate “lost after a guess” from “lost after a false proof.” The second result points to reasoning you can correct. See the beginner guide for the basic safe-reveal rules.
Try the next run
Use one idea from this guide in the Minesweeper player. Its game page includes controls and edition/source details.