10 FOR A=0 TO 15
20 POKE 54296,A
30 FOR B=1 TO 100
40 NEXT B
50 NEXT A
60 FOR A=15 TO 0 STEP -1
70 POKE 54296,A
80 FOR B=1 TO 100
90 NEXT B
100 NEXT A
110 GOTO 10