623



     players will be black.
     In GTIA mode nine, you have 16 different luminances of the
     same hue. In BASIC, you would use SETCOLOR 4,HUE,0. To
     see an example of GTIA mode nine, try:

     10   GRAPHICS 9: SETCOLOR 4,9,0
     20   FOR LOOP = 1 TO 15: COLOR LOOP
     30   FOR LINE = 1 TO 2
     40   FOR TEST = 1 TO 25: PLOT 4 + TES
        T, LOOP + LINE +  SPACE: NEXT TEST
     45   NEXT LINE
     50   SPACE = SPACE + 4
     60   NEXT LOOP
     70   GOTO 70: REM WITHOUT THIS LINE,
        SCREEN WILL RETURN TO GR.0

     In GTIA mode ten, you have all nine color registers available;
     hue and luminance may be set separately for each (it would
     otherwise allow 16 colors, but there are only nine registers). Try
     this to see:

     10   N = 0: GRAPHICS 10
     20   FOR Q = 1 TO 2
     30   FOR B = 0 TO 8: POKE 704 + B, N
        * 16 + A
     35   IF A > 15 THEN A = 0
     40   COLOR B
     45   A = A + 1: N = N + 1
     50   IF N > 15 THEN N = 0
     60   NEXT B
     65   TRAP 70: NEXT Q
     70   POP: N = N + 1: FOR Z = 1 TO 200
        : NEXT Z
     75   GOTO 30

     GTIA mode eleven is similar to mode nine except that it allows 16
     different hues, all of the same luminance. In BASIC, use
     SETCOLOR 4,O,luminance. Try this for a GTIA mode eleven
     demonstration:

     10   GRAPHICS 11
     20   FOR LOOP = 0 TO 79: COLOR LOOP:
        PLOT LOOP,0: DRAWTO LOOP,191: NEXT
         LOOP
     30   GOTO 30

     You can use these examples with the routine to rotate colors,
     described in the text preceding location 704. GTIA mode pixels
     are long and skinny; they have a four to one horizontal length to
     height ratio. This obviously isn't very good for drawing curves