The perpendicular opening

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Why it is called perpendicular

Black's opening move f5 flips e5 and leaves a row of three black discs across rank 5. White then answers with the only move that flips down the d file, d6, which turns d5 white and stacks three white discs on top of each other.

One line runs across, the other runs down. They meet at a right angle, and perpendicular is the word for that. The diagonal and parallel families are named the same way, from the shape White's three discs make.

Every named line runs through c3, c4 or c5

Black's five legal replies all sit on the c file. Two of them, c6 and c7, have no named continuation anywhere in the catalogue. The other three carry all 39 named perpendicular openings between them.

c3, the Tiger group

The Tiger is 1. f5 d6 c3 d3 c4, and it is probably the most studied opening in the game.

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The Tiger keeps its name for another thirteen moves. The Mainline Tiger, 18 moves long, is the longest sequence in the catalogue and shows how far a well-trodden line can be mapped out.

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Off the same c3, Black can play g5 instead of joining the Tiger, which is the Ganglion. Later Tiger branches carry the names Brightwell, Leader's Tiger, Stephenson, Kung, No-Kung, COMP'OTH, Aubrey, Tamenori, Ishii and Rose-BILL, all listed below with their moves.

c4, the Cat group

1. f5 d6 c4 is the second branch, and its names are the shortest in the book: the Cat, the Italian, the Swallow and the No-Cat, with the Berner and the Sakaguchi running deeper off the Cat.

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c5, the Rose group

The third branch produces the Horse, the Mimura, and the long, heavily analysed Rose: 1. f5 d6 c5 f4 e3 c6 d3 f6 e6 d7.

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The Rose then splits again into the Greenberg, the Flat, the Rose-Birth, the Rose-birdie, the Rose-Tamenori-Kling and the Brightstein, among others. Shorter cousins off the same c5 move include the Ralle, the IAGO, the Bhagat, the Inoue and the Shaman, which the Danish federation named the Danish.

One route to each name

The perpendicular family holds 39 names in 39 move sequences, one each. The diagonal family is not like that: nearly every diagonal opening has two move orders, because the position three moves in is a mirror image of itself.

After 1. f5 d6 no symmetry survives at all, so every position in this family has exactly one route to it. If you are reading a game record and the moves match a perpendicular line, there is no second order to check.

What the perpendicular feels like to play

Perpendicular games usually stay in the middle of the board longer than diagonal ones. Fewer discs are pushed onto the edges early, so the game turns on mobility, keeping more legal moves than your opponent, rather than on edge tactics. That makes it a friendlier family to learn with, since the mistakes it punishes are the ones you can reason about.

Keep reading

• All Othello openings, the full index and how the families work.
• Diagonal openings, White answers f5 with f6.
• Parallel openings, White answers f5 with f4.
• Opening strategy, what to aim for in the first ten moves.
• Play a perpendicular opening, paste any sequence above into the board.