Line-Making Games: Gomoku, Connect6, Connect Four, Quarto and YINSH

The shortest rules, and the first to be solved

The win condition takes a single sentence: be first to arrange your pieces into a line of a given length. No ranks, no piece types, mostly no capturing. A child learns it at a glance — which is why it has been invented independently many times around the world.

But short rules have a price. Free-style Gomoku was proved a first-player win in 1993; Connect Four had already been solved completely in 1988, with the first player forcing a win by opening in the centre column. The shorter the rules, the smaller the search space, and the sooner a computer gets to the bottom of it.

So the design history of this family is really one question asked over and over: keep the rule that a line wins, and make the game unpredictable again.

Five repairs, five eras

Gomoku — forbidden moves (settled in the late 19th century). Black loses on a double-three, a double-four, or an overline; White plays unrestricted. This is the most direct patch: if the first player is too strong, lock him alone. The cost is that the rules stop being one sentence, and beginners most often lose by stepping on their own restriction.

Connect Four — gravity (1974). You choose a column and the existing height chooses the square. That one change compresses free two-dimensional placement into a one-dimensional choice, and for the first time makes “I was forced to build a platform for you” a tactic.

Quarto — take away the choice (1991). The sixteen pieces each carry four attributes, a line counts by shared attribute rather than ownership, and the piece you must place is handed to you by your opponent. A radical step: it splits choosing a piece and placing it between two people.

YINSH — make winning weaken you (2003, GIPF series). Every five markers you connect costs you one of your own rings, and rings are your mobility. A rare piece of negative-feedback design: the closer you get, the less you can do.

Connect6 — change the tempo (2005). Back to the purest form with no extra machinery: after the opening move, each player places two stones per turn. Since both sides now add stones at the same rate, the advantage is cancelled structurally and the rules remain a single sentence. Proposed by I-Chen Wu in Taiwan, it is the most elegant answer this lineage has produced so far.