Four in a row

Rules

Dark moves first. Each turn you choose a column that is not full and your disc falls to the lowest empty space. Four discs of your colour in an unbroken line, horizontal, vertical or diagonal, win at once. If all forty-two spaces are filled without a line, the game is drawn.

How to think about the grid

• The centre column belongs to the most possible lines. Start there and keep a presence in it.
• A threat is an empty space that would complete your four. A threat is only useful when the space below it is filled, or when your opponent is forced to fill it.
• Count rows from the bottom. As a general rule the first player profits from threats on odd rows and the second player from threats on even rows, because of the way the columns fill up at the end.
• Never drop a disc directly under a space where your opponent would complete four. Leave such columns alone for as long as possible.
• Build threats one above the other in the same column. When the opponent blocks the lower one, he gives you the upper one.

A plan for the first moves

• Open in the centre column. If the computer opens there, answer on top of its disc or right next to it; both keep the middle contested.
• Keep your discs connected, so that each new disc belongs to two or three possible lines at once.
• Before every move, look at each column and ask what happens if your opponent plays there next. Giving him a winning space directly above your own disc is the most common way to lose a game that looked even.

Frequent errors

• Playing on the edges early. An edge disc belongs to few lines.
• Watching only horizontal and vertical lines while the diagonal quietly fills up.
• Blocking a three that cannot be completed anyway and wasting a tempo.

The computer at this table

Computer analysis has shown that the first player can force a win by starting in the centre. The Champion here searches the position exactly once about a dozen discs are on the grid, so from that point it does not miss a forced win or a forced defence.