Keturi

Two players, one set of sixteen bricks, and a rule that turns the whole game over: you never place a piece you chose. You take one out of the pool and hand it across the table, and your opponent has to find a socket for it. Then they pick yours.

No two bricks in the set are alike. Each one stands short or tall, is laid up square or round, is bored straight through or left whole, and came out of one of the two brickyards you ordered the set from. Four bricks that agree on any one of those four traits, standing in one of the patterns, end the game — and it goes to whoever set the fourth one down, however the other three got there.

That is all of the rules, and it takes a minute to teach. Noticing the trap you just handed somebody takes rather longer.

FOUR RULE LEVELS
Each level keeps every pattern of the levels below it and adds a family of its own.
• Level 1 — rows, columns and the long diagonals. 10 patterns.
• Level 2 — adds the 2x2 squares. 19 patterns.
• Level 3 — adds the wider squares, such as the four corners. 24 patterns.
• Level 4 — adds squares standing on a corner, which are the hardest to see. 30 patterns.
The higher levels leave far less room for a draw. Level 1 is where you learn the handover; by level 4 a board with four bricks on it is already dangerous. If you like, a four has to be called: miss yours, and it stands there while the game goes on.

ACROSS THE TABLE, OR AGAINST THE COMPUTER
Two people at one device, taking turns. Or one person and a computer that plays at three strengths: easy takes a four when it is handed one and otherwise plays loosely; medium never hands over a winning piece while it has a choice; hard looks several moves ahead, and further as the board fills. Or watch two computers play each other.

A PUZZLE A DAY
Every day there is one puzzle, the same for everyone with the app: a position a few bricks in, and exactly one right move — the socket that makes four, or the one brick in the pool your opponent cannot win with. Argue it over a table.

LEARN IT IN A GAME
A lesson walks you through your first game with a coach at the table, pointing at the bricks and the sockets as it goes. Turn on the winning-cell hint while you are learning, and look any finished game over again move by move.

A SET YOU LAY UP YOURSELF
Before the first turn you choose the two brickyards the set is ordered from — nine yards, from bone to cinder — and then the table it is played on: the slab cut as an octagon, a hexagon, a dodecagon, a round or an oval; sockets sunk octagonal, chamfered or square; the screed floated in any of ten mixes, from a pale gypsum to a dark ferrous; and a course of brick laid round the edge as a kerb, in any of the yards, or no kerb at all. If two yards are hard to tell apart, the second set can be laid in Flemish bond instead, so the difference is in the brickwork and not only in the colour.

BUILT, NOT DRAWN
Every shape on the table is generated as the game runs rather than loaded from a file: the chamfers, the corbelled cap that steps out at the top of every brick the way a chimney is stepped out, and the bore cut through a brick in its own section — square through a square brick. The board is a slab of screed with sixteen sockets formed in it, not a grid printed on a face, so an empty cell is a hole and a filled one is a brick seated in it. Drag to turn the table a little when you need to read a diagonal.

A BOOK OF GAMES
Every finished game goes into the records, with seventeen things worth doing marked off as you do them. A game left half-way is there to pick up next time.

IT ANSWERS THE WINDOW IT IS GIVEN
It reads best in landscape, but nothing is locked to it. The rail sits beside the board in a wide window and under it in a tall one.

WHAT IT IS NOT
There is no online play. There are no ads, no accounts, no in-app purchases and no tracking of any kind. Nothing leaves the device, and the game works with no connection at all.