mode 21
      x=50
      repeat
        wait 1
        rem repeat
        rem keyb=inkey(0)
        rem until keyb<>-1
        colour 128+15:colour 0
        print tab(x,0);"@"
        colour 128+0:colour 15
        vdu 23,7,0,2,16;16;8;:rem scroll up 2, scroll down 3
        x=x+(-1^rnd(4))
        if x=0 then x=45
        if x>45 then x=45
      until false