Numbridge — Rules

Domains

Domains is the variant of Numbridge where nothing has to be connected. The 9×9 field and the digits 1–9 are the same as in Bridge, the structure of the game is in the basics, but the goal is different: divide the field into blocks and take them.

The goal

A block is nine cells. A block goes to whoever has taken more than half of its cells, that is five out of nine. Givens belong to nobody by themselves, but a claimed given is as much your cell as one closed by a correct digit, and it counts towards the block.

The field has nine blocks. The winner is the one with more blocks.

A block where nobody holds five cells yet counts as undecided. An equal count of blocks in mid-game is perfectly normal and never becomes the result: play continues until one player has more blocks than the other could reach even by taking every undecided block. A draw in Domains is possible only by agreement, with the "Draw" button, as in the other games of the club.

A block scoreboard is shown next to the board: how many blocks each player holds and how many are still undecided. On the board itself, a resolved block is outlined along its border in its owner's color — blue or red; an undecided block stays without that outline until one player holds five of its cells. When the game ends — played out or ended early — the blocks that decided the outcome are outlined more strongly. Here are those nine blocks on a map of the field: s marks the first player's blocks (blue), r the second one's (red), ? the undecided ones. Blue holds four, red three, two are contested:

   s   s   ?
   r   s   r
   ?   s   r

The 1-2-2 order

In a game where every cell counts the first move is worth a lot, and Domains evens it out not with a pie rule but with the turn order: the first player makes a single move, and after that each player moves twice in a row.

move   1    2  3    4  5    6  7    8  9
who    A    B  B    A  A    B  B    A  A

When you still have the second move of a pair, the table says "One more move in this pair". A pair is an opportunity: with one cell you take away your opponent's edge in a block, with the other you lock it in for yourself.

The clock counts each move separately: the second move of a pair gets its own full limit. The price of running out, however, is the whole pair at once — miss the limit and the turn goes to your opponent, with no second move of the pair.

There is no pie rule here: nobody takes the first stone.

Ending early

The game ends as soon as the outcome is settled — there is no point counting the field out to the end. That happens when one player has more blocks than the other could reach even by taking every undecided block: five blocks against two with two undecided, for example.

So a game of Domains is longer than a game of Bridge, but usually shorter than a filled field: about six dozen moves.

What that feels like in play

A cell placed in the wrong spot is not just lost tempo but a cell handed over in someone else's block. Contested blocks, where both players hold four cells, are what decide the game; a block where you already hold five needs no defending — it is yours for good.

Usual room settings

Rooms are configurable; in the club, Domains is set up like this:

• a 9×9 field, from 22 to 34 givens, 30 by default;
• claiming a given costs one tile, and the hand is refilled afterwards;
• blocks regular or irregular — your choice in the seek; an irregular block also has nine cells, and a majority is still five;
• candidate highlighting allowed;
• 45 seconds per move, 20 minutes per game.