What is Hatari?
Hatari is a two-player tile placement game played on a board made of
Einstein "hat" tiles — a 13-sided shape discovered in 2023 that tiles
the plane in a pattern that never repeats. Every game is played on a
unique board. No two games are ever the same.
The rules are adapted from Go, one of the oldest strategy games in the
world. The goal is to control more of the board than your opponent by surrounding territory
and capturing their tiles.
The Board
The board is a region of aperiodic hat tiles. Unlike Go's regular grid, tiles here have
varying numbers of neighbors — some share borders with 4 others, some
with 6 or more. This asymmetry is part of what makes every game feel different.
Board sizes
81 tiles — quick game (~15 min)
156 tiles — medium game (~30 min)
361 tiles — full game (~60 min+)
Tile colors
Blue — Player 1
Green — Player 2
Dark — empty
Orange border — atari
How to Play
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1
Blue (Player 1) goes first. Players alternate placing one tile per turn by clicking any empty tile.
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2
Liberties. A tile's liberties are the empty tiles directly bordering it. Connected tiles of the same color share their liberties — they form a group.
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3
Capture. If you surround an opponent's group so it has zero liberties, the entire group is removed from the board. Captured tiles count toward your score.
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4
Suicide is illegal. You cannot place a tile that would leave your own group with zero liberties — unless doing so captures opponent tiles first (which restores liberties).
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5
Ko rule. You cannot make a move that recreates the exact board position from before your opponent's last move. This prevents infinite loops.
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6
Pass. Instead of placing, you may pass your turn. Two consecutive passes end the game.
Atari
When a group is reduced to just one liberty, it is in atari —
shown with an orange border. It can be captured on
your opponent's very next move. Watch for groups in atari and either rescue them (by
extending the group to gain more liberties) or ignore them if they aren't worth saving.
Scoring
The game ends when both players pass consecutively. Final score is the sum of three things:
Stones
Every tile you occupy on the board at the end.
Territory
Empty regions completely enclosed by your tiles. Shown as a faint tint at game end.
Captures
Tiles you removed from the board during the game.
The player with the highest total wins.
Strategy Tips
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→
Connect your tiles. Isolated single tiles are easy to surround. Larger connected groups are much harder to capture.
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→
Watch tile connectivity. Some tiles on the aperiodic board have more neighbors than others. High-connectivity spots are harder to surround and easier to defend from.
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→
Think about territory early. Placing tiles to enclose empty regions is often more efficient than trying to capture opponent tiles directly.
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→
The board changes every game. Familiar patterns from previous games won't always translate — read the board you have, not the one you remember.
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→
Don't fill your own territory. Placing tiles inside an area you already control reduces your territory score. Leave it empty unless you need to block.
Controls
| Click tile | Place your tile (only on your turn) |
| Alt + click | Inspect a tile — shows its neighbor count, group size, and liberties |
| Pass button | Skip your turn without placing |
| ← Lobby | Return to lobby (does not resign — you can rejoin) |
About the Hat Tile
The "hat" monotile was discovered by David Smith, Joseph Samuel Myers, Craig S. Kaplan,
and Chaim Goodman-Strauss in 2023. It is the first known shape that can tile an infinite
plane using only itself — with no gaps, no overlaps, and no repeating pattern.
Mathematicians had searched for such a shape for over 60 years.
The word einstein comes from the German ein Stein — "one stone" or "one tile."
The name Hatari plays on both the tile's shape and the Go concept of atari.