spriteshift3.asm

    push ix
    push iy
    push hl
    push bc
    push de

 	 ld	ix,#0 ; set up ix to point at stack
	 add ix,sp

    ld d, 15 (ix) ; aY
    ld e, 14 (ix) 
    ld hl, #(_yofs)
    add hl, de
    add hl, de
    push hl
    pop iy

    ld h, 13 (ix) ; aX
    ld l, 12 (ix)

    ; divide aX by 8
    srl h
    rr l
    srl h
    rr l
    srl h
    rr l
    push hl
    pop bc

    ld sp, iy ; set stack to point at yofs table

; Setup done
    pop hl
    add hl, bc ; add x-offset
; skip, background completely visible
    inc hl
    ld a, (hl)
    and #143
; skip or:ing since value was 0
    ld (hl), a
; skip, background completely visible

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #254
; skip or:ing since value was 0
    ld (hl), a
    inc hl
    ld a, (hl)
    and #1
; skip or:ing since value was 0
    ld (hl), a
; skip, background completely visible

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #252
; skip or:ing since value was 0
    ld (hl), a
    inc hl
    ld (hl), #0 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #127
; skip or:ing since value was 0
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #252
; skip or:ing since value was 0
    ld (hl), a
    inc hl
    ld (hl), #238 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #63
; skip or:ing since value was 0
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #252
; skip or:ing since value was 0
    ld (hl), a
    inc hl
    ld (hl), #247 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #31
    or #128
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #240
; skip or:ing since value was 0
    ld (hl), a
    inc hl
    ld (hl), #253 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #31
; skip or:ing since value was 0
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #240
    or #3
    ld (hl), a
    inc hl
    ld (hl), #255 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #31
    or #128
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #240
    or #3
    ld (hl), a
    inc hl
    ld (hl), #191 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #31
    or #128
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #240
    or #7
    ld (hl), a
    inc hl
    ld (hl), #255 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #63
; skip or:ing since value was 0
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #224
    or #3
    ld (hl), a
    inc hl
    ld (hl), #254 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #127
; skip or:ing since value was 0
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #224
    or #3
    ld (hl), a
    inc hl
    ld (hl), #250 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #127
; skip or:ing since value was 0
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #224
    or #2
    ld (hl), a
    inc hl
    ld (hl), #254 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #127
; skip or:ing since value was 0
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #240
    or #3
    ld (hl), a
    inc hl
    ld (hl), #190 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #127
; skip or:ing since value was 0
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #248
    or #1
    ld (hl), a
    inc hl
    ld (hl), #156 ; shortcut: background completely masked
    inc hl
    ld a, (hl)
    and #127
; skip or:ing since value was 0
    ld (hl), a

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #248
; skip or:ing since value was 0
    ld (hl), a
    inc hl
    ld (hl), #0 ; shortcut: background completely masked
; skip, background completely visible

    pop hl
    add hl, bc ; add x-offset
    ld a, (hl)
    and #252
; skip or:ing since value was 0
    ld (hl), a
    inc hl
    ld a, (hl)
    and #103
; skip or:ing since value was 0
    ld (hl), a
; skip, background completely visible

    ld sp, ix ; Restore stack pointer
    pop de
    pop bc
    pop hl
    pop iy
    pop ix