The Past Master Club
ZX81

5		REM ZX81 REM "JOYSTICK PROGRAM WITH MEMORY SAVING METHOD":
10		LET Q=1
15		LET F = Q - Q
20		LET R = Q + Q
25		LET B = F
30		LET X = F
35		LET Y = F
50		PLOT X, Y
55		UNPLOT X, Y
60		IF INKEY$="4" THEN LET B = Q
70		IF INKEY$="3" THEN LET B = R
80		IF INKEY$="9" THEN LET D = A
90		IF INKEY$="0" THEN LET D = Q
100		IF B = Q THEN PLOT X, Y
105		IF B = R THEN UNPLOT X, Y
110		LET X = X + ((INKEY$="8" OR (INKEY$="7" AND D = F)) AND X < 62) - ((INKEY$="5" OR (INKEY$="6" AND D = Q)) AND X > F)
115		LET Y = Y + ((INKEY$="7" OR (INKEY$="6" AND D = Q)) AND Y < 42) - ((INKEY$="6" OR (INKEY$="8" AND D = Q)) AND Y > F)
120		IF INKEY$="G" THEN LLIST
122		IF INKEY$="Z" THEN COPY
124		IF INKEY$="B" THEN LPRINT
130		GOTO 50
140		STOP