Sprouts — the rules of the game

Sprouts

Dots are joined by lines, each line getting a new dot; no dot may have more than three lines, and whoever cannot move loses.

A few dots are drawn on paper. A move is a line between two dots, or a loop from a dot back to itself, followed by a new dot placed on that line.

There are three restrictions, and none is complicated: lines never cross, neither each other nor themselves; no more than three lines leave any dot; and a line touches no dot but the ones it starts and ends at.

It looks as though this could go on for ever — every move adds a dot, after all. But every move spends as well: two line-ends go into the endpoints and two more into the new dot. Free ends grow scarcer, and the game must end. Whoever has nothing left to draw loses.

Players2

CategoriesPaper-and-pencil games

ObjectiveLeave your opponent with no legal move.

Rules of Sprouts

The start

A few dots — — are placed on the paper. How many is agreed beforehand; three or four make a short game.

A move

The player does two things in succession:

draws a line — from one spot to another, or from a spot back to itself as a loop;
puts one new spot on that line.

The new spot is no different from the starting ones and plays on equal terms.

Restrictions

A line crosses no other line and does not cross itself.

A line passes through no spots but the ones it starts and ends at.

No more than three lines may leave one spot — that is the . A loop counts as two: it leaves the spot and returns to it.

A spot placed on a new line already has two lines — one each way — so only one more may be drawn to it, and a loop cannot be added to it at all.

End of the game

The player who cannot draw a legal line on their turn loses.

Worth knowing

How many spots to start with is agreed: the more there are, the longer the game. It is also played the other way round, with the last player to move counting as the loser. The number of moves in a game is bounded by the rules themselves, though: it cannot run for ever.