Planning over speed — read the minefield, flip the board, fence off territory, play a real game of Go. Free, in your browser.
Strategy games reward the move you make three turns from now. Read the field in Minesweeper, turn the board to your colour in Reversi, claim squares in Dots & Boxes, or play a real game of Go on a 9×9 board.
There is no clock forcing your hand, so these are slow, satisfying games you can put down mid-match and come back to. The computer opponents scale from a gentle warm-up to a genuinely tough match.
Set a board, send the link, and see whether a friend can solve it more cleanly than you did.
Minesweeper is filed here, and nothing is playing against you. It is a solitaire information game: the field is fixed before your first click, and every number on it is a true statement about its eight neighbours. The other four are adversarial, and the useful way to tell them apart is by what a good player is required to value. In Ultimate Reversi it is mobility — mid-game material is a trap, and the disc count you lead by in move thirty means close to nothing. In Dots & Boxes it is parity: late on, the board resolves into chains of boxes, and the only question left is who will be forced to open the next one. In Go 9×9 it is life and death — a group needs two genuine eyes, and corners give the least room anywhere on the board to build them. In Tic Tac Toe ZAP it is threat construction, because the win length scales with the board: the larger grid asks for double threats and open-ended runs that the classic 3×3 never had space to contain.
In four of these games the ladder is not the puzzle getting harder, it is the opponent getting better — deeper reading, a sharper evaluation of the position. Minesweeper is the exception, and the same seven words mean mine density instead: around 10 per cent of cells at Beginner, about 16 per cent at Medium, which is the density classic Minesweeper shipped with, and 30 per cent at Cyborg. A stronger opponent is always beatable by playing better. A 30 per cent minefield will occasionally hand you a true coin flip that no amount of skill removes, and knowing which kind of difficulty you are facing changes how you should feel about losing.
Tic Tac Toe ZAP on a large board: the most familiar rules on the page attached to the most surprising game behind them. Then Dots & Boxes, which looks like a doodle and hides one of the sharpest endgames in casual gaming. Reversi next, once you are willing to give away discs on purpose. Go last — 9×9 is the size real Go schools start students on, and it keeps a game to minutes instead of hours. Minesweeper fits anywhere; if you like its deduction but would rather nothing exploded, Nurikabe is the same reasoning without the bomb.
The Go opponent runs Monte Carlo tree search, and that method has an appetite problem: more playouts make it stronger and also make it slower. My call was to cap it with a per-move time budget, enforced at every level, so strength scales through how efficiently the engine spends a fixed budget rather than through how long it keeps you waiting. The trade-off is real and I will name it — the top level is weaker than it could be if I let it think. I took that deal anyway, because an opponent that stalls kills a game far faster than one that occasionally blunders.