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71 lines
1.1 KiB
NASM
Executable file
71 lines
1.1 KiB
NASM
Executable file
; b = new colour for BG colour 0 (usually white) for 4 frames
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ChangeBGPalColor0_4Frames:
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call GetPredefRegisters
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ld a, [rBGP]
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or b
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ld [rBGP], a
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ld c, 4
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call DelayFrames
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ld a, [rBGP]
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and %11111100
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ld [rBGP], a
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ret
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PredefShakeScreenVertically:
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; Moves the window down and then back in a sequence of progressively smaller
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; numbers of pixels, starting at b.
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call GetPredefRegisters
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ld a, 1
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ld [wDisableVBlankWYUpdate], a
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xor a
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.loop
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ld [$ff96], a
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call .MutateWY
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call .MutateWY
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dec b
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ld a, b
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jr nz, .loop
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xor a
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ld [wDisableVBlankWYUpdate], a
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ret
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.MutateWY
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ld a, [$ff96]
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xor b
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ld [$ff96], a
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ld [rWY], a
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ld c, 3
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jp DelayFrames
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PredefShakeScreenHorizontally:
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; Moves the window right and then back in a sequence of progressively smaller
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; numbers of pixels, starting at b.
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call GetPredefRegisters
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xor a
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.loop
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ld [$ff97], a
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call .MutateWX
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ld c, 1
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call DelayFrames
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call .MutateWX
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dec b
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ld a, b
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jr nz, .loop
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; restore normal WX
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ld a, 7
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ld [rWX], a
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ret
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.MutateWX
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ld a, [$ff97]
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xor b
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ld [$ff97], a
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bit 7, a
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jr z, .skipZeroing
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xor a ; zero a if it's negative
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.skipZeroing
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add 7
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ld [rWX], a
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ld c, 4
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jp DelayFrames
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