PROGRAM LISTING: 84-11/PRETTY.ACT

PROC pretty()
   DEFINE key="Peek(764)<255"
   CARD sc
   BYTE wsync=$D40A,
        vertcnt=$D40B,
        color0=$D01A,
        color1=$D018,
        counter, chgcolor,
        upcolor, i, loop,
        downcolor
   Graphics(23)
   Poke(764,255)
   sc=PeekC(88)
   SetBlock(sc+75*40,40*20,255)
   SetBlock(sc+37*40,40*20,255)
   SetBlock(sc,40*20,255)
   DO
   FOR counter=1 to 9
      DO
      upcolor=chgcolor
      downcolor=chgcolor
         DO
         wsync=0
         color0=downcolor
         color1=upcolor
         upcolor==+1
         downcolor==-1
         UNTIL vertcnt&$80
         OD
      OD
   chgcolor==+1
   UNTIL key
   OD
RETURN