Why a riverbed?

Five in a row has always been played with stones. So we put the stones back where stones come from: the bed of a shallow river. One side plays smooth dark river stones. The other plays pale sea glass, the frosted bits of old bottle that the water rounds off over the years.

When someone lines up five, the pebbles in that line catch the light one after another, and a little fish swims along it. The computer players are river animals.

A bit of real gomoku history

The game comes from Japan, where it is called gomokunarabe. Go means five, moku is a counting word for pieces, and narabe means to line up. It was played with the black and white stones of the board game go, on a go board. The board used to be 19 by 19. Today it is usually 15 by 15.

Japanese records trace the game back to the Edo period, around the middle of the 1700s. The oldest gomoku book that can still be checked was published in 1856. You will read online that the game is thousands of years old, or that it came from China, but we couldn’t find good evidence for either. By the 1880s it had reached England, where it was known as go-bang.

Whoever moves first has a big advantage. On 6 December 1899, the journalist Kuroiwa Ruikō gave the game a new name, renju, meaning “connected pearls”, in his newspaper Yorozu Chōhō. Renju later added rules that limit the first player, Black. In 1994 the Dutch computer scientist Victor Allis proved that in the free game on a 15 by 15 board, the first player can always win with perfect play.

Pebble Five uses the simple free rules. Five in a row wins, and so do six or more. There are no forbidden moves. You always move first against the computer, which is a real head start.

The three river friends

• 🐸 Tadpole: takes a five when it sees one and stops yours when you are one pebble away. It only notices an open three about half the time.
• 🦞 Crayfish: always blocks open threes and builds its own lines, but it never looks past the move it is making.
• 🐦 Kingfisher: hunts for chains of fours and threes that win by force, makes sure you can’t do the same, and looks a few moves ahead.

How to play

• You play the dark river stones and go first. Tap or click a point where two lines cross to set a pebble there. Five in a row wins, across, up and down, or on a slant.
• On a phone, “tap twice to place” is on to start. The first tap shows a faint pebble and the second tap sets it.
• Pick a 13 by 13 river or an 11 by 11 stream, which is easier to tap on a small phone.
• Stars for a win count your own pebbles: fewer pebbles, more stars. Each friend’s targets are on the ladder. Using undo takes one star off. Beat a friend to meet the next one.
• Pick 2 players to take turns on one device. On a keyboard, use the arrow keys and Enter.
• Sound is on to start. Tap 🔊 to mute, or 🎵 for music.
• Earn 3 stickers in this game for your QuickBOP sticker book.

Tips

Know your fours. A four is four pebbles that need one more to make five. If only one point finishes it, the other player can block that point. An open four has both ends empty, so there are two points that finish it. Nobody can block both, and the game is over.

Block open threes at once. An open three is three in a row with room to grow at both ends. Next turn it can become an open four. So when the other side makes one, block an end straight away. A three with one gap in it counts too.

Make two threats with one pebble. A single pebble that makes a four and an open three at the same time usually wins. The other player has to block the four, and then your three becomes an open four. Two open threes at once work the same way.

Your turn

The river at the top of this page is clear and still. Start with the Tadpole, work your way up to the Kingfisher, and play.