BONE IDLE (16K ZX81)
by W A George, Stenage, Hertfordshire
from Your Computer (April 1983), Page 151

This is a program for a 16K RAM ZX-81. It is widely recognised that the
prime function of a computer is to make life easier for us all, but to
program one to play Patience for you must be the ultimate in laziness. My
excuse is that the computer can play faster than me, and it does not cheat.
The game is Clock Patience.

The computer will shuffle the cards and set them out in a clock-face
pattern on the screen  it deals at random from a new pack each time which
amounts to the same thing. Should the computer succeed in getting the game
to come out, it will stop with message 9/380 and CONT NEWLINE will start it
off again.

If it fails, it will display the Ace that stopped it in the bottom left of
the screen, and after a pause try again. Remember this is a program with
hidden data stored within it, so to restart from a listing use GOTO 11.

The computer plays at about two games per minute, and if such haste makes
you dizzy, an extra line:

    265 PAUSE 100

will slow things down a bit, or if you dislike the screen jump caused by
Pause there is room for a dummy loop at that part of the program. On the
other hand, if your patience is limited delete line 175, and insert:

    222 SLOW

This will speed things up by not displaying the cards until after they have
been set out.

The computer starts play with the top card from the one o'clock pile. If
you wish it to start in the centre, change line 230 to read:

    LET X=13

and alter the first subscript of the arrays in line 370 to read 13 also.

If desired, the program can be altered to delete line 335. Replace it with:

    235 PRINT AT (20+1**1),0;D$
    236 PRINT AT (20+1**1),0;"  "

This will cause the card in the bottom left of the screen to flash, and
demonstrate a novel use of the ** function to cause a slight delay  a good
idea gleaned from somebody else's program, and deserving to be more widely
known.
