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⌂ ∞ ▽ Elite on the 6502

Drawing the screen: FadeColours

[NES version, Bank 3]

       Name: FadeColours                                             [Show more]
       Type: Subroutine
   Category: Drawing the screen
    Summary: Fade the screen colours towards black
  Deep dive: Views and view types in NES Elite

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * FadeColoursTwice calls FadeColours
             * FadeToBlack calls FadeColours
             * FadeToColour calls FadeColours




.FadeColours

                        ; We are about to go through 31 entries in the colour
                        ; palette at XX3, fading each colour in turn (and
                        ; ignoring the first entry, which is already black)

 LDX #31                ; Set an index counter in X

.fade1

 LDY XX3,X              ; Set Y to the X-th colour from the palette

 LDA fadeColours,Y      ; Fetch a faded version of colour Y from the fadeColours
 STA XX3,X              ; table and store it back in the same location in XX3

 DEX                    ; Decrement the counter in X

 BNE fade1              ; Loop back until we have faded all 31 colours

                        ; Fall through into SetPaletteColours to set the view's
                        ; palette to the now-faded colours from the XX3 table