Reversi

Reversi is the classic disc-flipping board game — the one also sold as Othello — played here against four opponents who are not four re-skins of one bot. Each one weighs the board by a different thing and is blind to a different thing, and they are ordered so that each is harder than the one before it. You always play dark, the legal moves are marked, and a match takes a few minutes.

The rules are one sentence: place a disc so that a straight line of your opponent’s discs is trapped between it and another of yours, and every trapped disc flips. That single rule produces the game’s famous trap — taking the most discs early is usually losing, because discs you own now are discs your opponent can flip later. The pieces that matter are the ones that cannot be flipped at all, and a disc in a corner is the only one that is safe by geometry: flipping needs enemies on both sides, and a corner has no both sides.

That is why the corners are marked on the board and why the squares beside them are the most dangerous places to play. It is also why the four opponents feel different rather than merely harder. The Glutton takes the biggest bite available every turn, which is exactly the mistake the game is built to punish, and it is the gentlest opponent here. The Vise ignores discs entirely and squeezes the number of moves you have left until you are forced to hand it something. The Mason builds unbroken walls along the edges. The Anchor runs for corners, will not give one back, and is the hardest of the four.

There is no timer and nothing to buy. Undo takes back your move and the opponent’s reply together, so you can explore a line without restarting. Beat an opponent and the next unlocks; the board remembers who you have already beaten.

Tap or click a marked square to place a disc — you always play dark. Every disc caught in a straight line between your new disc and one of your own flips to your colour, in all eight directions. Marked dots show your legal moves; if you have none your turn passes automatically, and the game ends when neither side can move.

The corners are marked because a disc in a corner can never be flipped — which also makes the squares next to them the most dangerous on the board. The undo button takes back your move and the opponent’s reply together. Four opponents sit on the ladder, each harder than the one before: the Glutton grabs the most discs it can, the Vise strangles your options, the Mason builds unbroken edges, and the Anchor runs for corners and never gives one back.