;=================================================================================
; Quick palette fade
;=================================================================================

.section "Quick fade" free

FadeInScreen:

    halt                   ; wait for Vblank

    xor a
    out ($bf),a            ; palette index (0)
    ld a,$c0
    out ($bf),a            ; palette write identifier

    ld b,32                ; number of palette entries: 32 (full palette)
    ld hl,PaletteBuffer    ; source
 -: ld a,(hl)              ; load raw palette data
    and %00101010          ; modify color values: 3 becomes 2, 1 becomes 0
    srl a                  ; modify color values: 2 becomes 1
    out ($be),a            ; write modified data to CRAM
    inc hl
    djnz -

    ld b,4                 ; delay 4 frames
 -: halt
    djnz -

    ld b,32                ; number of palette entries: 32 (full palette)
    ld hl,PaletteBuffer    ; source
 -: ld a,(hl)              ; load raw palette data
    and %00101010          ; modify color values: 3 becomes 2, 1 becomes 0
    out ($be),a            ; write modified data to CRAM
    inc hl
    djnz -

    ld b,4                 ; delay 4 frames
 -: halt
    djnz -

    ld b,32                ; number of palette entries: 32 (full palette)
    ld hl,PaletteBuffer    ; source
 -: ld a,(hl)              ; load raw palette data
    out ($be),a            ; write unfodified data to CRAM, palette load complete
    inc hl
    djnz -

ret

;---------------------------------------------------------------------------------

FadeOutScreen:

    halt                   ; wait for Vblank

    xor a
    out ($bf),a            ; palette index (0)
    ld a,$c0
    out ($bf),a            ; palette write identifier

    ld b,32                ; number of palette entries: 32 (full palette)
    ld hl,PaletteBuffer    ; source
 -: ld a,(hl)              ; load raw palette data
    and %00101010          ; modify color values: 3 becomes 2, 1 becomes 0
    out ($be),a            ; write modified data to CRAM
    inc hl
    djnz -

    ld b,4                 ; delay 4 frames
 -: halt
    djnz -

    ld b,32                ; number of palette entries: 32 (full palette)
    ld hl,PaletteBuffer    ; source
 -: ld a,(hl)              ; load raw palette data
    and %00101010          ; modify color values: 3 becomes 2, 1 becomes 0
    srl a                  ; modify color values: 2 becomes 1
    out ($be),a            ; write modified data to CRAM
    inc hl
    djnz -

    ld b,4                 ; delay 4 frames
 -: halt
    djnz -

    ld b, 32               ; number of palette entries: 32 (full palette)
    xor a                  ; we want to blacken the palette, so a is set to 0
 -: out ($be), a           ; write zeros to CRAM, palette fade complete
    djnz -

ret

.ends