What this game is
Ataxx is a game about infection. Your pieces do not capture enemy pieces, they convert them, and one well-placed move can turn half the board around.
A game starts with two pieces in opposite corners and almost always ends with a full board. Early on a move barely matters; by the middle one move flips four or five enemy pieces at once, and the score swings until the very last square.
Rules
- The board is 7×7. You play blue, the computer plays red, you move first.
- Pick one of your pieces, then an empty square no more than two squares away in any direction, diagonals included.
- A move to an adjacent square is a clone: the original piece stays, so you gain a piece.
- A move two squares away is a jump: the piece relocates and your total does not change.
- Every enemy piece next to the square you moved into — horizontally, vertically or diagonally — turns into yours.
- A player with no legal move loses immediately; passing is not allowed.
- When the board is full the player with more pieces wins. A tie goes to the computer.
How to play better
- Clone more than you jump: a jump adds nothing to your army and hands the initiative to your opponent.
- Corners and edges are gold. A corner piece can only be attacked from three sides instead of eight, so corner gains are nearly permanent.
- Do not stretch into a thin chain: a lone piece among enemies is a gift, it flips together with its neighbours.
- Count the position after your opponent replies, not the score right now. Taking five pieces is pointless if seven come back.
- At the end it is not mass that decides but the last move: whoever fills the final square often flips the result.
A bit of history
The game was created in 1988 by two British programmers, Dave Crummack and Craig Galley, under the name Infection. Versions for the home computers of the day were written but never released commercially, and the rights went to the publisher Virgin Mastertronic.
In 1990 it surfaced twice at once: as the arcade machine Ataxx from Leland — the name that stuck — and as Spot: The Video Game, starring the red dot from the 7UP logo. The arcade version added maps with blocked squares, and in 1992 Hexxagon moved the same mechanics onto a hexagonal board.
This version follows the game that ran on this site from 2005 and keeps its quirks on purpose: a two-piece start, instant defeat when you have no move, and a tie awarded to the computer. Classic Ataxx starts with four pieces and lets a player without moves simply pass.
About the levels
Easy is the original 2005 algorithm carried over untouched: it looks one move ahead and takes whatever gains the most pieces right now.
Hard searches three moves ahead but only counts pieces. It has no idea corners are valuable, which is exactly how you beat it.
Expert searches five moves deep and weighs position as well as material: a corner is worth more than the centre. Beating it takes work.