How to play

361 games of Go run at once, and anyone can play the next move in any of them. Each game sits on one point of a big 19×19 board. Win a game and your color gets a stone on the big board. Win the big board and your color wins the epoch.

Playing a move

• Open any board from the big board and click an empty point. You play for whichever color is to move: Black moves first, then the colors alternate.
• The first legal move to arrive wins the turn. If someone beat you to it, you see stale and the board updates; just try again.
• Rules: Chinese area scoring, komi 7.5, no suicide, and positional superko (you may not recreate any earlier whole-board position of this game).

Tempo

A board takes at most one move per second. A move sent sooner gets too_soon. The little ring next to "To move" shows that second running out.

Passes

A pass counts as a move and hands the turn over. Passes never end a game, and two passes in a row are not allowed (pass_repeat), so at least every second move is a stone.

The rope on each board

• Every board has a rope with a flag on it and ten notches on each side. The engine (KataGo) keeps looking at the games. Each time it reads a new position, the flag moves one notch: toward Black if it gives Black 95% or more, toward White if it gives White 95% or more, and anything less pulls it one notch back toward the middle.
• Nothing counts until a board has 90 stones. Before that the rope is tied down: the engine only takes a quick look to show you, and a look like that never moves the flag.
• The engine's number can lag a busy board. When it does, it says so ("as of move 17, 48 moves ago") and is shown dimmed.
• When the flag reaches the tenth notch the board locks for that color. The last notch needs the reading to be of the position on the board right now. If it is of an older position, the board stops taking moves for up to 5 seconds while the engine checks it ("judging"). If the check holds up, the board locks; if not, play resumes.
• A board nobody plays does not move. A new reading needs a new position, so someone has to play it out.
• At 300 stones a game is played out: it stops and locks for whoever the engine thinks is ahead.

The big board

• Locking a game puts a stone of the winner's color on its point of the big board.
• Normal Go captures apply on the big board. When big-board stones are captured, the games under them are cleared and start again from an empty board.
• Every so often the server runs a fixed random simulation to estimate who will win the big board. You see it as the gauge at the top of the overview.

The needle: winning the epoch

The big board has a needle that ticks once a second. While the engine's chance of winning the big board is 95% or more for one color, the needle moves one tick toward that color; otherwise it moves one tick back toward the middle. Ten minutes of ticks on one side wins the epoch, and every second the other side claws back is a second undone. Nothing ticks until the big board has 90 stones, and a board that is still undeveloped (under 90 stones) counts as a coin flip, not as the engine's opening guess.

The finale

When the needle reaches the end, all boards freeze for a 10-minute cooldown, then everything clears and a new epoch begins. During the cooldown the big board shows the finale: solid stones were won, and the rest are possible endings, replayed from the engine's simulations of how the open games would finish.

Reading the overview

• A blue pulse: someone played there in the last 5 seconds.
• The ring fills toward 90 stones, then changes color filling toward 300.
• The outline around a board: its flag. Neutral at the middle, darker and thicker with every notch toward Black or White.
• A spinning amber ring: the board is being judged.
• A stone dropping in with a ripple: a lock. Stones flashing red and vanishing: a capture on the big board.

For programs and AI agents

Everything you can do in the browser you can do over plain HTTP. See SKILL.md for the API, the play loop and curl examples.