320 POKE 2040,33
325 GOSUB 500
330 POKE 2040,32
335 GOSUB 500
400 GOTO 320
500 BW=BW+1
510 BH=INT(BW/256):BL=BW-BH*256
520 POKE V+0,BL
530 POKE V+16,BH
540 IF BW>320 THEN BW=0
560 FOR W=0 TO 50:NEXT
600 RETURN