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A complete chess-playing program and all packed into 1K of memory. The memory limit-ation means that certain details of the game have to be omitted: you can't capture en passant or achieve pawn promotion. The program is in machine code and loaded at the third try, but it only takes 25-30 seconds to load anyway.

There are two programs on each side and the choice of which is loaded determines the opening move, either white queens pawn or white kings pawn moved. Moves are entered number-letter of the piece to be moved followed by the number-letter of the square to move to. Only valid moves are allowed.

The ZX81 seems to choose its move by testing all possible moves and then selecting the move which captures your highest valued piece, if any. Although this makes it vulnerable to traps, it still produces play which needs some thought to beat. The screen display is small - one ZX character square equals one board square - and pieces are represented by letters, P, Q and K for example, in normal (black) and inverse (white). The display can cause confusion and I mis-takenly moved the wrong piece once or twice due to this.

The instructions are minimal. The rules and piece moves are not explained.

Ray Elder