Minesweeper

The rules as implemented here

Three classic layouts: beginner is 9 by 9 with 10 mines, intermediate 16 by 16 with 40, expert 30 by 16 with 99, matching the proportions Windows made canonical. Mines are placed only after your first click, and your first cell is excluded, so you can never lose on move one. Worth knowing: only that one cell is protected. Unlike some modern versions, the neighbors are not cleared for you, so a first click that opens onto a lone "3" is legal and normal. The timer starts on that first click and counts whole seconds. You win by opening every safe cell; flagging all the mines is not required, flags are bookkeeping for you, not the game.

The mines-left counter is simply the mine total minus your flags. It trusts your flags completely, so overflag and it will cheerfully mislead you, or even go negative.

Speed comes from chording

Clicking an already-open number whose flagged neighbors equal its value opens all its remaining neighbors at once. That is chording, and it is the difference between clearing a board and crawling through one. The standard rhythm is flag the certain mine, then chord the number next to it, opening three or four cells per click instead of one. The warning is built into the mechanic: chording executes your beliefs. If a flag is wrong, the chord opens the real mine and the game ends, which keeps speed honest.

The tip worth internalizing: learn the 1-2-1 and 1-2-2-1 patterns along walls. A 1-2-1 against an edge puts the mines under the 1s; a 1-2-2-1 puts them under the 2s. These two patterns resolve a large share of midgame walls instantly, with no counting, and recognizing them on sight is worth more than faster clicking. On touch screens, toggle Flag mode and taps place flags; tap it off to open cells. Desktop right-click flags as usual.

What good times look like

The site saves a best time for the 9 by 9 board only, so records stay comparable. Beginner boards fall in well under a minute once chording is habitual, and the real skill measure is intermediate and expert, where reading efficiency dominates. Be aware that classic minesweeper, this version included, sometimes ends in a genuine 50/50 guess, most often in corners or along the last unopened strip. Losing one of those is not a skill failure; the board simply did not contain the information.

Implementation notes

Opening a zero flood-fills the whole connected empty region and its numbered border in one go, which is why a lucky early click can rip open half the board. Mine placement is uniformly random with no solvability guarantee, so unlike our sudoku, a guess-free clear is probable but not promised. Flagged cells cannot be opened by any click, including chords, so a stray flag is a shield as well as a liar. Losing reveals every mine and marks the one that got you. Nothing leaves your browser: no accounts, no leaderboard, and your beginner best evaporates with your site data. The expert board scrolls horizontally on small screens rather than shrinking below usable tap size, a tradeoff chosen deliberately for touch play.