10 D=10

20 CLS: CURSOR 0: 

30 P=0: Q=AREAD(27)*8/164

40 GOSUB 200

100 FOR X=1 TO 640

110 Y=AREAD(27)*8/164

120 LINE 1,X,Y,P,Q,1

130 P=X: Q=Y: DELAY(D)

140 NEXT X

150 CURSOR 1

160 GOTO 20

200 ' background

210 FOR A=0 TO 640 STEP 32

220 FOR B=0 TO 200 STEP 10

230 C=7

240 LINE C,0,B,639,B,1

250 LINE C,A,0,A,199,1

260 NEXT B

270 NEXT A

280 LINE C,639,0,639,199,1

290 LINE C,0,199,639,199,1

300 RETURN