3D OXO (16K ZX81)
by A J Heathcote, Canterbury, Kent
from Your Computer (June 1984), pages 174-177

3D OXO is a three-dimensional adaptation of noughts and crosses. This
program is written in machine code for a 16K ZX-81.

The board displayed on the screen is a representation of a 4 by 4 cube. The
aim of the game is to complete a line of four crosses - in any direction -
before the computer gets a line of four noughts. The player may select one
of three levels of skill; level 1 is the easiest.

You will be asked first to choose your level of play and then to decide who
starts. At the beginning of each move, a cursor appears at the top
left-hand corner of the board. The keys 5 to 8 are used to move the cursor.
Shift 6 and Shift 7 will move the cursor to a different level  down and up
respectively.

Move the cursor to the square of your choice, then press NEWLINE to enter
an X. The computer makes its move in the same way, entering a O in one of
the squares. To stop the game, enter S instead of making your move.

A complete line of noughts or crosses is indicated by a row of flashing
squares. If no result is possible, the computer declares a draw.

A copy of this program is available on a cassette, price 3, from A J
Heathcote, 11 Norman Road, Canterbury, Kent CT1 3LX. [Although probably
isn't available any more. PF]
