Full ZX-81 Chess in 1K: "One further point should be explained. It is
not possible to give a good opening or finish to
the game because that would require slightly
more code than we have available in the 1K
game. We actually have only 672 bytes.
The game, therefore, starts off with the
computer playing white and either the King's
pawn or the Queen's pawn moved forward one
position. The following describes the machine
code and techniques used in the creation of my
1K ZX-81 chess program."